Openbook

http://a.viary.com/home

Recently i stumbled upon this site on Image editing. Its pretty cool looking .Try it yourself.Its features include Peacock, a special effects creator, and Toucan, a color manager etc.
This sites Phoenix online image editor now includes an option to install a Firefox extension that will allow you to perform screen captures and more.

location : http://vconvert.net/
This cool looking  site converts FLV videos from Youtube to WMV or 3GP format and provides link for downloading.

UNIX System Calls and Subroutines using C
location :    http://www.cs.cf.ac.uk/Dave/C/CE.html

It is an excellent site for intermediate and advanced C programmers.
The course contents include

Using UNIX System Calls and Library Functions
Running UNIX Commands from C
using execl(), fork(),wait(), exit()
Piping in a C program
IPC
Socket programming
Thread programming etc….