One does not simply walk into the Steam free-to-play catalog—or at least that's what Turbine seems to think. Better late than never, they've brought their free-to-play epic fantasy MMO Lord of the Rings Online to the Steam store this morning.
The game is available as a free download, but Steam is also offering a fairly enticing $15 bundle that gives you three of the early zones' quests, $15 of cash shop currency, an XP boost, and an exclusive grey horse mount. If you enjoy the game and hit the point where you're considering buying one of the three zones unlocked in this bundle (Northdowns, Evendim, and Misty Mountains), I'd highly recommend buying this bundle instead.
LOTRO was one of the first western MMOs to have success with a free-to-play model that gives players access to the entire world for free, with the option to purchase quest or features content in chunks as they play or subscribe to get everything included.
Turbine's been very good about consistently updating it with new content that expands the main storyline through the Shire, Moria, Isengard, and--in the new expansion coming in September-- Rohan, the land of horseback riders and Helm's Deep that is adding mounted combat to the game.
The game also has a fairly active roleplaying server that hosts regular events like music festivals that take advantage of the game's robust instrument system that lets you write and perform music note-by-note.
Turbine's other main free-to-play MMO, Dungeons & Dragons Online , has not been added to Steam at this time.