The biggest expansion to date for EVE Online will be released March 10, 2009, according to CCP. The announcement came on the last day of Fanfest. Eurogamer has the details:
The focus of the expansion will be "true exploration," with players using new skills and modules to travel through wormholes into all-new, unconnected space. There they will find unique stellar phenomena and the resources and artefacts that will lead to the third level of technology in the game universe, Tech 3 - the first such update since Tech 2 was introduced back in 2004. The star feature of Tech 3 will be modular, customisable ships. Instead of providing each faction with one or two new ships each, CCP will provide each with a template that comes in five sections, with five options in each.
One bit of clarification is needed: the Eurogamer article incorrectly states the amount of permutations possible for ship combinations. As seen in this thread, the correct amount is 3,125 (five sections with five options each). Or, CCP Mephysto mentions in the thread that 12,000 combinations may be possible if you consider all four races. The full Eurogamer article can be found here or below.