Plugin for firefox:http://fzami.mozdev.org/index.html
It puts the prayer times down there in the status bar in the far right corner. it also can notify you however many minutes you want before or after the time for the next prayer comes in and can play athan too if u wanted.
Islamic Finder's Athan software:http://www.islamicfinder.org/athanDownload.php
Guidance - Prayer Times for Mac OS X
Guidance is a prayer times application for Mac OS X that plays the Adhan when it is time to pray salah. Designed to be simple and elegant, Guidance sits in the menu bar and shows a countdown until the next prayer. When it’s time for prayer, Guidance displays a Growl notification and plays the adhan. Guidance stays out of the way while providing you with current prayer time information.http://guidanceapp.com/download/?a=get_guidance