Allow me to highlight some free MIT-licensed, open source applications using Thinlet by Katherine Rhodes.
ServerWatcher.
A graphical server monitoring tool. You can enter the url of a web page and a character string you want it to look for and ServerWatcher will check the page at regular intervals. When something is wrong ServerWatcher will give you a red light, make a "ding" sound, and log all failed attempts. Windows users can send an ICMP ping to a server too. Useful for keeping an eye on a box that doesn't have a web server running
Carterpillar.
Caterpillar is a simple textual RSS feed aggregator. It's goal in life is to be small, quick, simple, and allow for the easy addition of other XML feeds, like OPML, Atom, or anything else. Right now it only has RSS readers.
EpochTime.
An epoch date to human readable converter. Also allows you to generate an epoch date for a given calendar date and lets you convert a number of seconds or milliseconds into HH:MM:SS:mm time. All calculations support milliseconds or seconds.
More @ http://tools.masukomi.org