Home: Ancient Dell Precision 370, 2.8GHz P4, 4GB memory, 40GB boot/system disk, 1TB data disk, 2TB external backup drive - used as a file server, Kubuntu 4.04.4 LTS on it right now. The most important software on it is my Logitech Media Server for streaming my music library to work
Work: Dell Precision 490, 2X Xeon 5160, 16GB, 2X Dell 20-in monitors, CentOS 7, KDE.
Plus all the damn servers and other desktops I need to support. At least we finally got rid of the last VAXstations this past year...
For software, mostly Firefox for browser although every now and then it pisses me off and I switch to Chrome (and then, after a while, Chrome pisses me off and I go back to Firefox). Emacs/XEmacs is editor-of-choice for anything big, vi or nano for quick edits. Most used software is probably Konsole. VirtualBox and/or QEMU/KVM for VMs. Whatever random software I need to support/answer questions about on any given day. X11vnc/vncviewer gets a pretty good workout.