Diptera.info

In my search for some information about a thick-headed fly, I ran across this site.  Diptera.info has tons of great information, pictures, links, and a great forum.  The forum is great if you are trying to determine exactly what species of fly (or midge) you have found.  And you'll especially love the site if you're a bug geek.  There are a bunch of other bug geeks lurking in the forums all the time too, so you should feel right at home.  And be sure to check out the photos; many of them are absolutely amazing.