Here's a collection of online utilities that you might find useful once in a while.
If you do find any problems with the programs mentioned below, please feel free to contact me.

HTML ValidationCheck any webpage for errors
Your DetailsShows what your IP address, browser and proxy are
String Encode/DecodeConvert a string to and from different encodings
Squid blocked sitesSquid blocked sites
Group TrackPrivate instant messaging
Eve calculatorCelebrate every day!
Basic UNIX CommandsTo get you started
File PermissionsHow they work and how to change them
Using hdparmHow speed up your IDE hard disk