… for a woman who is single, in her mid-forties, and just bought her first house? Previous to this, she was living in one half of a duplex, so it’s not like she doesn’t have household stuff, but I am so excited for her that I’d like to give her something she’d like and find useful. Ideas? She also has several dogs and a yard that needs fixing up.
A lawn mower or weed-eater would be nice…
If she’s a do-it-yourself type, a Home Depot gift card would be great. If she needs help with the yard, a local landscaper could give you an idea of what he could do for how much, and you could give her that.
Also, a small toolbox will be invaluable to a new homeowner. If she has the basics, she can get through nearly any trauma, at least until the professionals get there.
This sounds corny, but a photo of her front doors (past and present) matted and framed, is very cool.
A Dildo ? 
Sorry… couldn’t resist. You say she already has her home stuff… but something might be old or clumsy. Figure out what she might like having a brand new model of. Especially kitchen stuff if she likes to cook. New home… new stuff. Just make sure she isn’t overly attached to her old frying pan or whatever.
Howzabout a flag pole kit and flag for her front porch. Kinda symbolic considering some parts of the world women aren’t allowed to own anything.
A seedling tree would be a nice gift to watch grow or , if she has a mailbox on a post, a new mailbox with her numbers on it.
If all else fails one word will suffice: Gnomes. 
If she’s a do-it-yourself type, a Home Depot gift card would be great. If she needs help with the yard, a local landscaper could give you an idea of what he could do for how much, and you could give her that.
Also, a small toolbox will be invaluable to a new homeowner. If she has the basics, she can get through nearly any trauma, at least until the professionals get there.
This sounds corny, but a photo of her front doors (past and present) matted and framed, is very cool.
Whoa, deja vu.
My then-boss gave me a push mower for my (very tiny) yard. That was nice.
If she doesn’t have one, every homeowner needs a power drill.
If it’s more a Gesture than an Actual Gift (i.e., I don’t want to spend more than $10 or $15), I’ll get a nice, but not super-expensive, vase (think Target, Ikea), and give that with a bunch of flowers.
Second the Home Depot (or Lowe’s, or whatever’s near her) gift card. UncleBill and I just bought a house a month ago and have spent about a million dollars at HD already.
If you don’t like giving gift cards, a friend gave us a lovely bird feeder, which I really appreciated. We have a big back yard, and it will be nice to have birdies to watch in the yard.
Another possibility, esp. if you’re handy – offer to go over and spend an afternoon helping her with whatever. This would be great even if you’re not particularly handy – moving stuff around, unpacking books, putting together Ikea shelves, etc., are all time-consuming projects. There are a lot of projects that are easier or at least less annoying if you’ve got two people.
Third HD/Lowes/etc gift card. There are several small repairs/modifications that I need to make to my new condo that I’ve been putting off. Like the closet door that fell off its tracks, one of those metal belay thingies for the blinds so the cats don’t use the cord for a toy, etc, etc.
Bread and salt are the traditional house warming gift.
I usually get my friends an embosser with their new address. They typically run about 40 dollars.
If that is too steep, you can always buy return labels.
One of those do-it-yourself books that explains what to do when the faucet leaks, or when the hot water heater goes out.
It will require some research, but you could try to find out if local adult evening education offers a course on basic household repairs and then pay her tuition. The one that I do through the local community college is 6 weeks, 2 hours per night every Monday, and covers electrical, plumbing, fitting molding, installing ceramic tile, repairing drywall, and such.
danceswithcats, if your class talks about what to do for a leaky faucet or when the water heater goes, I am so there. Unless you live, like, far away. In which case I’ll just wish I were there.
I’m lazy. Unless I know the person and their taste really well, I give a house plant or wine (and sometimes a wine rack as well).
If you know her well, you can truly personalize the gift. For instance, if she’s into interior design, you could pay for a consultation, or a subscription to a design magazine, etc. I’d be reluctant to give something so specific without knowing whether the recipient would truly appreciate it, however.
Yep.
But I have given bread or scone mix (or for your friend’s case, perhaps dog biscuit mix) in place of “bread” and nice sea salt (or bath salts) for salt.
Sure does. I’ve been collecting old plumbing fixtures for students to tear apart and work on for about 5 years, and yes, there is a complete toilet removed from service and pressure washed for everyone to monkey with. Very hands-on. 
Hundred dollar bills!!
Are you serious? 'Cuz I thought I came up with that up my own self–I’ve tended to give a housewarming gift of bread (local artisanal bread), salt (nice sea salt), fire (beeswax tapers), and wine (something decent–generally tokaji azsu, 'cuz that’s what I tend to have on hand), wrapped in a nice linen cloth in a basket.
Dang. Now I don’t feel original any more.