Re: I'd like to do something nice for Wifey, but I'm broke...
You could get her a simple card, and write some of your own sentiments inside it. A few flowers - handpicked off the side of the road would get you bonus points (at least, it would with me! lol). Both of those are very inexpensive.
There's websites that will allow you to create a website for free (webs.com is one of them, but if you just google "free websites", you'll get a ton), you could create a website on which you proclaim your love for her, and whatever else you want to put on there. Give it a url that doesn't indicate what it is and then tell her you want her to check out this website.
Cook her dinner, her favorite meal. Serve her, and clean up after.
Showing love and appreciation, romance, none of that has to cost much, if it costs anything at all. For me anyway, the thought that goes into something means much more to me than the thing itself. My boyfriend bought me a stand mixer for Christmas our first Christmas together. My friends and family all saw it as something that shouldn't be a Christmas gift and indicating that he expected me to be in the kitchen all the time. I saw it as he knew me so well, after only a few months together, that he knew how much I loved baking and that I would appreciate a stand mixer that would make the mixing process much quicker and allow me to make much more. That gift meant so much more to me than anything else he could have given me. Keep that in mind as you try to think of what to do for her - even if it seems out of the ordinary, or something others might not like, if you know *she* would, go for it.