I'm a little surprised that no one has mentioned webfsd (http://linux.bytesex.org/misc/webfs.html), which I use to solve this problem (specifically, as webfs -r .).

Caveats:

- I'm sure showoff is better if you're firewalled.

- It's probably slightly easier to share just one file in a directory with showoff, but this could be remedied with a script that made a temporary webfs root and symlinked the shared files thither.