What I'd do with a research lab, part 3:
Test a pet theory regarding Dark Energy
Working hypothesis: There is a fairly elegant modification to gravity that may explain Dark Energy, and that current MOND theories do not touch upon.
We've known since 1929 that our universe is expanding, but in 1998 we discovered that our universe is actually accelerating in its expansion. This flies in the face of accepted understandings of gravity and the Standard Model of quantum mechanics, neither of which allow for any reason that the universe should be expanding. We've come to call this force "Dark Energy" because it pushes the universe apart, just as the presence of energy does, yet we're unable to observe it.
I've been kicking around an idea of how Dark Energy might arise. It is, of course, a low-probability hypothesis, but there aren't really any front-runner theories on Dark Energy, the magnitudes involved in my hypothesis make sense, it's unique (to my knowledge), it'd be an elegant way to solve the problems of Dark Energy and inflation if it worked, and I think diversity of effort is very valuable in science. So I'd indulge myself. It's sort of a waiting game at this point since there isn't that much data on the historical expansion rate of the universe, which is really necessary to test these sorts of theories (elegant doesn't mean correct), but I do believe gathering such data is one of the highest priorities in cosmology.
I can hear a physicist in the background snort at my presumption. Quiet, you- get your own blog. :)
 Some theories which attempt to explain Dark Energy are listed at the Wikipedia page; physicists are also exploring a promising new option tying Dark Energy, Dark Matter, and inflation to supersymmetrical particles. A reasonably good overview of the new option may be found at Ars. If you're wondering what all this Dark Energy stuff is about, Wikipedia and NASA are good places to start.
Edit 11-7-07: It occurs to me I should put forward something falsifiable in this post.
My theory suggests that a universe with homogeneously distributed mass, in entropic equilibrium, and with no expansion momentum would (setting aside quantum fluxuations that would immediately bring it out of such equilibrum, and contrary to all gravitational theories I'm familiar with) not collapse due to gravity. Rather, a "dark energy" term would arise which would precisely balance gravity. As the distribution of mass becomes less homogeneous, the dark energy term would naturally increase relative to gravity's effect on the universe's topology.