Es.gy reminds you of the links you stumble upon by email.
OutStanding is a web based app to remind you to stand up at a certain time interval in your browser.
Cut Your Time helps set alarms to remind you of your tasks using various options.
Mater runs a 25 minutes timer followed by a 5 minutes break in the menu bar of your Mac.
RestStop reminds you to take a break after you have worked for a certain time on your PC.