Linux Mint Debian Edition (LMDE) is my current favourite linux distribution. It is built on Debian, which has the reputation of being the most stable, secure and well-tested linux distribution, and is extremely user-friendly.
LMDE comes free of charge and is fully compatible with Debian. A default installation packs most of the applications that a typical user is likely to need. If your computer is connected to the internet, thousands of other applications could be installed via its package manager.
If you are up for some adventure, try Debian. You will find it here.