Sometimes it is useful to use online compilers when your computer is not available. These websites will run your code a little slower, but something is better than nothing.
No login (but available):
CodeChef - has a clean interface, supports a variety of languages, can download code, can go full-screen, supports custom input, and has limited auto-completion
Ideone - supports more than 60 languages, can download code, has no auto-completion
Login required:
Repl.it - has a clean interface, supports more than 50 languages, can download code, supports reading from a file, supports auto-completion, and has multiplayer mode (see Compilers - Collaborative)
Well, this is the only compiler I was able to find online that supports being embedded. This should be a good place to test things quickly especially when you don't have access to your downloaded IDEs.