Cryptic offers three free-to-play games: Champions Online (superheroes), Neverwinter (D&D v4.0 rules, approximately), and Star Trek Online (which now has storylines for Starfleet, the Klingon Defense Force, and the newly-formed Romulan Republic). And unlike many other such offerings, these really are free to play - you can go all the way to level cap without ever spending a dime. (I know, I did so on one of my STO characters, Vice Admiral Jonathan Sills, currently commanding USS Hans Asperger.)
If you play Champions Online, be aware that for some unknowable reason, they thought people might be overwhelmed with too many choices at the beginning, so about 85% of the costume options for your hero are hidden until you reach 10th level with your first character. It starts looking a lot better then...
_________________
Sodium is a metal that reacts explosively when exposed to water. Chlorine is a gas that'll kill you dead in moments. Together they make my fries taste good.