if i were to run a server, id run Slackware 12.0 and then write a little script (or modify the current one) and run vsftpd
it's fast, stable, and like it's name says, very simple
however, there are a lot of fans here of Ubuntu and some other distros, so if you want to use this as a primary help site, then id probably go with Ubuntu. and last but not least, the BEST way to get proficient in linux is to USE IRC!
there are soooooo many good ppl out on IRC that can help you with any distro. it's been by far my best resource.