shit i just put the keywords in the filename

Excessive, obsessive folders are probably your best bet. From what I remember there aren't any good image metadata solutions yet.

Honestly, Picasa's probably about as good as it gets. I use iPhoto on Mac (inb4 derisive laughter) which is about the same, but I like the interface more, plus nested albums are handy and smart folders are great if you use keywords extensively. Keyword management could be better though.

I actually liked Microsoft Expression Media pretty well, but it's not free, it wasn't very fast, and it only wrote the metadata to the images for certain formats. Mostly JPEG. I know it didn't write the metadata to PNGs, and I can't recall for certain that it would even import them. But I was using Expression Media 2. I don't know if 3 is out.

ACDSee has an image library-type program that also does tagging as I recall, but it costs actual dollars, was slow compared to Picasa, and while its organizational features were better (nested albums) it didn't really offer much advantage over Picasa otherwise. Like Expression Media, I don't recall whether or not it wrote the tags to the image files themselves, either.