If you're asking in a general forum, you're probably new to Linux. So I would point to Linux Mint, as it's more user friendly and has a common interface that is more Windows-like, and well supported but not bleeding edge updates. Ubuntu would be the next, but it has some "issues" with who controls it (Canonical). That being said, it's well supported too as far as when installing things. Mint is an offshoot of Ubuntu, so they're related. They both have different install version also, depending on how old or limited your machine is.

There are plenty of others, but these are the two that will usually be mentioned for someone starting out.