Our current servers:
Intel processors: 2.4Ghz(orange) 3.2Ghz(tangerine) 2*3.6Ghz(clementine)
3ware RAID (RAID1 for orange, RAID5 for tangerine and clementine)
1GB DDR2 RAM (4GB for clementine)
1Gbps ethernet ports (connection to the internet is also 1 Gbps)
Passive cooling for reliability (orange only)
Active resource monitoring
Debian Linux (we follow the "testing" release schedule)

Our servers have redundant internet connections as well as battery and diesel power backups.