Bioware has announced that Rise of the Rakghouls, The Old Republic's first major content update, is now live. Your client should download the update the next time you start it.
In addition to a number of bug fixes and balance changes, the slightly belated 1.1 patch introduces two new pieces of high-level group content. The first, Kaon Under Siege, is a brand new, level 50 Flashpoint group combat misson. The second addition is an expanded version of Karagga's Palace, which adds in four new bosses to the game's second launch Operation, more than tripling its length.
Other noteworthy changes include level 50 bracketing for PvP WarZones and added support for anti-aliasing. You can find the exhaustive list of patch notes over on the game's official site.
The 1.1 patch is the first of many content updates that BioWare intends to release throughout the year. Game Update 2, currently slated to go live sometime in March, will add more new content and game systems. Some of the planned features include a full Legacy system, Guild Banks, and PvP rankings. On the content side, BioWare will be giving players a new Flashpoint that continues the story of Kaon Under Siege, as well as a new planet called Denova that features an Operation and WarZone.