Lighttpd is light, fast, and unbloated, much like its chosen logo: a paper airplane. It has great Perl, Python, PHP, and even Ruby/Rails support through FastCGI. Though Apache can certainly do everything it can, lighttpd does it with significantly less overhead and memory usage, making it especially ideal for high-bandwidth websites which work primarily with large 1MB+ files.
My only qualm is the lack of .htaccess (a huge selling point for Apache) and its confusing and non-directory specific mod_rewrite implementation.
I really like the fact that the config file is much cleaner and easier to understand than some of the legacy HTTP servers. Its web serving, redefined! :)
The down side is that its FastCGI (i.e. Perl) handling is still pretty weak. Someone please show me how to run Perl CGI quickly on this web server!