There isn’t exactly a great deal of variety in this weekly Humble Bundle offer, but if you like space sims (and the X series from Egosoft in particular) that probably won’t bother you one bit. Yes, the bundle is basically all of the X series games to date, from X: Beyond the Frontier to X3: Albion Prelude.
Any old donation whatsoever will get you X: Beyond the Frontier, X-Tension, X2: The Threat and X3: Reunion, and at least $1.00 USD will ensure that you’ll have Steam keys to use for those games. Beat the average price ($6.00 USD right now) and you’ll also get X3: Terran Conflict, X3: Albion Prelude and some sort of mysterious ‘superbox’ of bonus bits. As well as soundtracks for Albion Prelude and the forthcoming X: Rebirth.
That’s a lot of uses of the letter X, right there. As is always the case, you can spread your donation (whatever the amount) between charity (the EFF and Child’s Play,) the developers Egosoft and Humble Bundle themselves.