Nethaera announced new pre-Cataclysm data is available in live servers. The file is 1.58GB, and can be downloaded while playing the game, or after closing World of Warcraft. Your download preferences can be found by clicking the options button on the bottom-left of the WoW Launcher.exe.

[BLUE]The next major content patch is coming and sets the stage for Cataclysm with many great new changes, updates, and pure epic fun. We’ve packed it to the brim with so many new things that this patch proves to be the biggest one yet. In order to smooth the way, we have started background downloading the first segment of data for this patch. People who use the Launcher and have background downloading enabled will automatically start receiving the data. Other segments of data are forthcoming over the next few days.

To make sure you are pre-downloading data, make sure to run the launcher and see text that reads “Data for the next patch is available.” You should then see a message indicating when data will be downloaded. Click “Options”, then “Downloader Preferences” to make changes to when you background download data.[/BLUE]