Last couple of nights I have hacked a generic URL-based cache for Gravatar, the globally recognized avatar. If you have been blogging or reading other people's blog, "gravatar" would not be foreign to you, as it has been implemented on many blog sites of various platforms. Gravatar Cache is an implementation to cache both positive and negative response. Moreover, if positive cache is served, PHP script is not invoked as cache is served directly from the web server.
I have also added gravatar onto the comments section of FuCoder.com, utilising the gravatar cache. Cache is served from another server -- not DreamHost but a VPS I rented from unixshell# running Gentoo + lighttpd. We'll see how it goes.