As well as the C/C++ interpreters I've mentioned in the past there is another way to
and run a C or C++ program. Just visit the website codepad.org
, select C or C++, paste in your code and click a button. There are eight other programming languages available as well, including D which I mentioned not so long ago. You can view what other people are trying out and there's a lot of C in that list!. Hopefully that's because of the language's popularity and not just because it's the first language alphabetically available!
Codepad is the brain child of Steven Hazel and he's quite keen to see if you can break the system. It uses the free public domain Geordi IRC bot to compile and run C/C++. I can't see it replacing compilers any day soon but if you just want to try something out quick, it doesn't get much easier than this!