My friend has had a seriously shitty week, and I’m trying to think of something I can do to cheer her up. I’m a great person to come to if you want someone to listen or for advice, but not in the making you feel better after something shitty happened catagory.
Rules: No balloons, chocolate, ice cream or flowers. Must be free or cheap, I’m broke as usual.
Help!
Spend time with her. Listen to her, commisserate. Maybe go out of your way to think of something to do for her she’d appreciate.
Seriously, I’ve never understood what the “stuff” thing is in cheering someone up. Particularly the balloons thing…
If you think she really needs stuff, how about loaning her all those books you’ve been meaning to. Or giving her some of your things she’d appreciate that you no longer do.
Or you could have a “do” Cook her dinner. Put on a movie she’ll like. Have a girly night where you let her soak in the tub while you clean her house, then give her a manicure and a pedicure.
Puppy time always works for me. Is there a puppy (or kitten, if that’s your thing) that she can borrow for a day or so? Even just an hour or two of playing with something furry and cute might help.
Send her a virtual flower bouquet, or one of those funny animated egreeting cards. You can google it to get the site URLs.
What about having a Monopoly marathon?
Stop by the library and pick up a book of ghost stories to read to each other.
Ducks.
I don’t know if you have access to ducks and a pond/lake, but feeding ducks is good therapy… especially if there are cute little baby chicks with them. Go to the store, buy a loaf of past-its-prime bread for $0.59 and go feed some ducks. But it might only work if she’s an animal lover…
EZ
I think people respond differently to different things. For those of us who appreciate words of affirmation, you can’t imagine how much they mean. If she’s like that, write down a list of 10 reasons why she’s so wonderful. Don’t make it humorous, make it sincere. If I got something like that, I’d be walking on a cloud all day. 
Why has nobody yet mentioned beer?
A 30-pack of cans is ten bucks. And that’s enough for the two of you to sit around, commiserate, poke fun, and laugh in uncontrolled drunken idiocy until the biggest problem you’ve got is the blinding headache on Saturday morning.
Beer? What about sweet hot monkey love?
Does your public library rent videos? Many libraries rent them for free or virtually free. Get some seriously funny movies or TV shows.
Then buy a bag of popcorn–real popcorn, not that microwave crap. Bring the movies over to her house and make her some popcorn. Then hang out and watch the silly movies and eat popcorn.
Really, it’s hard to stay in a bad mood with a pot full of popcorn popping away.
If you’re both comfortable with the idea, a backrub!
No beer, she doesn’t drink. The whole spending time doing girl stuff won’t work, we’re both in college and have young kids. Good ideas, though.
Lib’s suggestion is perfect. Thanks, I can never think of stuff like that. I’ll have to make her list a little funny, though.
Keep 'em coming folks. 
Send a card/postcard/letter. Doesn’t everyone LOVE “real” mail? The letter can say anything or nothing, something serious or something funny… You don’t have to buy a cheesy-ass card. Just get some paper and crayons and go crazy. (Don’t let not being able to draw stop you)
okay, it’s not free… it costs 37 cents. It’s a good “follow-up cheerup” because it takes a day or two.
Oral sex.
Or is she not that kind of friend?

Give her some babysitting time so that she can do errands or just pamper herself.
Have you tried a hug? They usually go a long way toward making someone feel better, and they’re completely free.
Alternatively, you could take her kids for the evening while she stays home and does girly stuff. Never underestimate the healing power of a long soak in a hot tub free of interruptions.
Go sit on the swings at a park. I find swinging (no, not that kind) to be relaxing but also fun. Makes you feel like a kid again!
I gotta tell you though, chocolate made my day better yesterday. Tis a shame it’s off the list. 
Or Whack-a-Mole.
There is nothing that a couple rounds of Whack-a-Mole won’t fix.
Let her win. She’s had a bad week.
Skee-ball might work. Or Dance Dance Revolution, depending on what you’ve got at the local arcade.
Is there any sort of private joke you can reference easily? I’ve gotten a big laugh out of potted meat before. Drooling on myself also works, depending on the day. These probably won’t work for you, but there’s got to be something small and cheap that will bring on the giggles. Crappie magazine, maybe?
Why don’t you tell her, “I know you’ve had a shitty week. I’d really like to indulge you a bit to cheer you up. We both know I’m broke, but I’ll do anything that you’d enjoy. We could talk, play, veg, or I could babysit so you could have an uninterrupted time in the bathroom or whatever you can think.”
The if she opts of the babysit, you could make a handprint or other little craft with the kiddos for her. It costs nothing to trace a hand and write I love(care, admire, appreciate) you, or whatever.