Operation Beachhead is the latest N7 Bounty Weekend from BioWare for Mass Effect 3's multiplayer mode, and it's running from April 6-10, 2012. Yes, that's a bit longer than a "weekend." There's also no explicit goal for this challenge; rather, all players will receive a +25% XP bonus in all multiplayer matches for the duration of the challenge. Note that this only applies to Xbox 360 and PC versions of the game.
There IS, however, a noteworthy thing to consider for Beachhead. The Mass Effect 3 multiplayer Operation's description reads: "Allied forces have matched krogan mercs and batarians with asari justicars for unconventional warfare. Their mission: to create resistance on Reaper-occupied planets to tie down local Reapers." I'll refer you back now to this rumored Mass Effect 3 multiplayer DLC post from March 13.
As you can see in the previous post's purportedly leaked image, a number of new races seem to be bound for the game at some point. Two Batarian classes (Solder and Sentinel), two Geth classes (Engineer and Infiltrator), a Krogan Battlemaster, and an Asari Justicar. Bear in mind that none of those have actually been confirmed.
Now look back at the description for Operation Beachhead. Isn't it interesting how it mentions Batarians, Krogans, and Asari Justicars? The Operation started last night and those classes don't seem to be available based on what I played, but perhaps they'll be added after the "weekend" is over? It's all speculation, but it certainly seems worthy of consideration.
Source: BioWare Blog