Thyme - The task timer for OS X.
XNote Stopwatch - Try the most feature-rich stopwatch and timer software on the net for free!
Hourglass - Hourglass is the most advanced simple countdown timer for Windows.
SnapTimer - SnapTimer is a simple, free, portable countdown timer for Windows.
Stopwatch - A Java countdown timer and stopwatch. Features a fullscreen and a resizable window mode.
LClock - Longhorn systray clock program