What cool stuff can I do with my server?

So I got a old AMD Athlon XP 2500+ PC, with 512MB Ram and a 40GB Samsung IDE Drive. I put Linux (Ubuntu Server 12.10 x86) on it, it runs just fine 24/7. At the moment I have a Apache2 Server running. Do you know what other cool stuff I could do with it? (I am from Germany, please excuse my bad english)

i keep an ftp running on my server and keep shared files on that so all the computers can access them.

A public Access FTP server with useful freeware like 7-zip, Ccleaner, Defraggler, Ramdisk, speccy, CPU-z, GPU-z, legacy and 7 32 and 64 version of Graphics drivers, realtek has ione single file for all their drivers, have it set to read only and broadcast it wirelessly, useful for people without a internet connection, but only let them access the server not your ISP connection, unless you want to

Set up ownCloud, its awesome.  No more having to trust a big company with all your files.  I was actually thinking about making a small tutorial since Logan, understandably, hasn't gotten around to it.  Let me know if you need help

Thanks for those reccomendations. I already have ownCloud, but the Sync-Client is very much Crap. it synced all my Music (about 12 GB) twice. And the bad thing about my internet connetion is that I only have 0.5Mbit/s Upload. Yea in Germany many pepole still use DSL.

I use mine for:

Minecraft

A seedbox

FTP

SSH 

And UPnP streaming

What do you mean with seedbox?

Put a web based torrent app on there:

  • Probably the best: https://code.google.com/p/rutorrent/
  • Deluge is also very nice: http://deluge-torrent.org/

Otherwise check out http://alternativeto.net/software/rtorrent/ for other ones.