Jacking off, though I tend to neglect the hobby when I’m dating. Sorry, Rosy.
The SDMB.
Running.
Softball. The only really essential piece of equipment is a glove, which i got for about $40. The league i played in used to run about $40 per season, plus $2 per week for umpire fees.
Now, i play in a pick-up group where there are no league fees. We just give the organizer a few bucks every now and then for new balls and replacement bases.
Music is both cheap and expensive. Once you own a serviceable instrument or instruments of your choice, then you don’t need to lay out significant sums of music on a regular basis. On the other hand, you still feel like a kid in a candy store when you go inside a guitar shop. I want…I want…I want! Sheet music is another expense if you are into classical playing. Even if you live near a good (usually academic) music library, and are allowed to use it, working with borrowed music is never as good as owning your own copy. But in general it’s a cheap pastime, unlike, say, golf where you have to pay green fees every time.
Free browser based flash games.
My favorite site is:
but armorgames is good too, and miniclip and addictinggames are more well-known.
Baking. Basic ingredients are pretty cheap, they’re usually on-hand and it makes your house smell wonderful. Plus you have a happy family, friends, coworkers, whoever you share the goods with. I take quite a few baked goods to my daughter’s elementary school, so I’m expecting her to bring home straight As. 
Gimp is FREE! That makes it better, in the context of this thread, anyway… Of course, if you already have Photoshop you’re set. I’m a rank n00b at photo manipulation so I can’t really give an informed opinion as to which is better, but so far Gimp has been able to handle anything my Photoshop For Dummies e-books have referenced.
Well, I have indifferent luck starting from seed (frost tends to come late in these here parts–and when you least expect it) so I get lazy and buy started plants, then I get involved in finding the fifty weirdest varieties of basil possible (I’ve never found seeds for lime basil, and have had little luck harvesting my own seed from grown plants) and I have Mutant Ninja Papyrus Grass From Hell With Attendant Rhizomes so it’s really easier in the long run to hire a rototiller every year–it adds up! I make all my trellises and other garden structures from tree trimmings and string so that’s cheap, and I rescue chunks of urbanite from Craig’s List when I need to make retaining walls and I’ve been collecting recycled windows and glass doors to make a cold frame and/or greenhouse but still, if you really wanna get crazy about it or you have a good sized yard gardening can turn spendy on you.
The front herb garden was mostly sweat and effort but it’s all perennial so it pretty much takes care of itself now with just weeding and mulching to keep up on. The two veggie gardens have their own challenges and need to be attacked separately–the rest of the yard is still mostly potential, but there’s gonna need to be some earth moving going on sometime soon… I also want a goat to keep the damned blackberry vines down, but that’s a whole 'nother level of expense!
Not if you go to the bait store and buy a batch of red wigglers to stock your worm farm–that’s about three bucks max and wigglers are easier to stomach handling than the gigantic earthworms I get around here–I’ve pulled suckers out that were eight inches long! I’m pretty sure I’d gag and gross out if I had to deal with an overloaded worm farm full of giant mutant earthworms.
After the initial outlays, biking and Kayaking are free. Birdwatching. Whittling. Learning to play the pennywhistle (pretty cheap for an instrument) Training my dogs to do tricks (competing is expensive, though)
Walking. Hiking. Winter tracking. Snowshoeing. Cross-country skiing. Botonizing. Origami. Word games and puzzles.
I’m broke, but happy!
I love to go hiking. Nothing decompresses me like some quality “alone time” out on the trail.
I also like to wander around and take pictures of random things in the neighborhood. I’ll just go out and photograph whatever catches my eye: store displays, seasonal decorations, flyers on lamposts, local flora and fauna, etc.
Walking is cheap, but I’m not really sure if I’d consider it a “hobby”.
Looking at property on-line. Real Estate web sites have been a huge boon to me. I’m no longer limited to small print ads or driving around. I can sit in the comfort of my own home and look at huge numbers of properties in many areas, complete with pictures. Oh, I can’t afford any of them, I just like looking.
Oh, I do that one, too! Only, I’m looking for my dream camping land.
Where’s George?. One can (like I have) spend money on custom-made stamps for this, or just use a pen. Regardless, it’s fun and addictive, and free.
Joe
Heh. I just closed the tab on the mls.ca website. I was looking at my neighbour’s back yard. And bedroom.
I’m going to take the dog for a walk next.
Amateur geology, although I’ve rarely had time for it lately. Not only do you get to see nature but you get to figure out why it is the way it is.
Also collecting microscopes and unusual magnifiers. There are some pricey ones but I try not to pay more than $10 per item.
Another one i’ve adopted recently:
Since we moved to San Diego, i’ve become something of a hobbyist seashell collector. I love walking the beaches and looking for shells that the waves leave behind. Of course, many of those in the sand are broken, the result of having been tossed around against one another, and against the sand and the rocks. But it’s nice to occasionally pounce on a nice, intact shell.
I haven’t yet done anything elaborate in order to find shells; they’ve all been collected simply by beachcombing. I also make sure that i don’t collect any shells that still have their little creatures living inside them. Not only am i not interested in killing something just so i can keep it’s house, but California law prohibits inter-tidal collection of live molluscs.
Some days there are virtually no shells at all, and some days there are quite a few. The best day i’ve had so far was a trip just last Friday to Coronado; the tide was low, the beach was quite deserted of people, and there were a few decent shells and lots and lots of sand dollars.
I just want to thank you, pedescribe, for getting me addicted to a new game. I read your post this morning and paid a visit to kongregate.com where I found Fantastic Contraption. What an amazing game.
I’ve always been fascinated by machinery and this game is close enough. So far I have managed to create fourteen contraptions that succeeded in moving the pink wheel/box to its goal. Of course, I created many contraptions that failed completely or in part before figuring out ways that work.
I’m going to kongregate right now but I stopped in to thank you for posting the link. I’ll get to those other two sites you named eventually. Thanks again.
Thin Ice
My signature:
Some folks will just never know the satisfaction of taking $3000 in
tools, and $2 in scrap and making a $7 part that can be bought for
$1.50
My Mom asked my why I was restoring a lathe, what could I possibly do with it? I said: “I’m going to make piles of shavings out of big metal blocks.”
After the outlay for a camera (of whatever quality you can afford), digital photography is a GREAT cheap hobby. I seldom print my photos, and use flickr to host them and share them.
I second/third/whatever gardening. Most of the time, if you’re interested in planting non-food or even food plants, you can get seeds/cuttings from a friend who gardens. My neighbors and I swap plants and cuttings back and forth all the time.
Oooh, birdwatching! I love bird-watching, and you can sometimes combine that with the digital photography hobby, too.
I agree. I’ve made stereoviews and panoramic pictures with my digital camera. Lots of fun and the results are impressive.
Jogging, digital photography, the odd skate on my inline skates, reading, watching way too much TV, writing, but that one is very seldom as I get annoyed at my inner editor.
I used to have a friend that was on the same page as me with regard to people watching. We would invent stories about everyone we watched. We came up with entire backstories for people in restaurants. It was one of my favourite things to do. I really need to find another person that likes that crap. I miss it.
Free public library.
Foraging, ala Euell Gibbons. Kids love to help look for nuts, berries or other good stuff.
Cooking.