I don't think much of the logo for this site, but the one I picked was public domain and at least topical (it's supposed to be a virus particle).
If you are any good with Photoshop, feel free to create something better. The logo is one of the few things you'll have to ask me to put in place, as it requires a file on the server to be edited directly. You should be able to upload it yourself though. The right size for a logo is 160x160px.