the most comprehensive BitTorrent search engine, with cross-referenced trackers. integrated XDCC, Fserve and NFO search for files on IRC (currently offline).
Mark Pilgrim's suggested apps for an Ubuntu desktop -- some quite good suggestions here, with lots of KDE goodness. I just wish amaroK was as user-friendly and usable as the amazing (but not well-maintained) JuK, though
an Operating System-level server virtualization solution, built on Linux. OpenVZ creates isolated, secure virtual private servers — VPSs (otherwise known as virtual environments — VE) on a single physical server enabling better server utilization and
simpy
