AMD FX-6300 with 16GB running Ubuntu and Apache. Doesn't take much to run a web server unless you have pretty big traffic. It also crunches BOINC work units from SETI@home, Rosetta@home, Einstein@home and World Community Grid on the side and earns a few Gridcoin...
RE: How to revive an old HP Proliant G6 server for Data Mining, Seed Node and Witness node.