I've been using www.vectorstock.com
for a while and buying vector art there. It's very cheap, as in $1 or $3 (some more). Which pretty much makes it a no-brainer for a lot of things.
I'd posted here about it:http://cynic.me/2011...mercial-use-cheaply/
There is a set in there that I've been using quite a bit, repeatedly. It's just simple glass buttons and letters, but it looks very nice and with a bit of editing effort, I've got an unlimited set of buttons.
They've got lots of icons as well, some better than others.
However, as it is vector art, you need to do some work with them, but it's worth it. I pretty much use PNGs whenever possible as they simply are far superior to BMPs or GIFs. You could make icons (ICOs) from the vector art, but I find that I rarely need ICO files.
Not free, but at $1? It's about as close as you can get.