Medicine
Jointly awarded to Sir John B. Gurdon and Shinya Yamanaka for "the discovery that mature cells can be reprogrammed to become pluripotent". You've no doubt heard of stem cells. Stem cells contain all the information to become any other cell - that is, they are pluripotent. Gurdon and Yamanaka showed that mature cells could act as stem cells. The Nobel prize being awarded to a controversial topic like stem cells may be an important step towards further research in the area.
Physics
To be honest, I look forward to the Physics Nobel prize more than the Chemistry prize, even though I am a chemist (at heart I'm probably more of a physicist, though). The prize this year went to Serge Haroche and David J. Wineland, for their work in quantum physics. My favorite quote from the interview with Serge Haroche is "I use atoms to study photons and he uses photons to study atoms". I won't go into too much detail. Instead I'll use the old fall back of to start the explanation...
I think he introduces a bit too much of a philosophical argument to the question (at least as far as the Nobel Prize goes) but that's better than any explanation I would give in that amount of time...
Chemistry
Robert J. Lefkowitz and Brian K. Kobilka shared the Chemistry prize for their work in G-protein-coupled receptors. I feel asleep when I heard the word protein, but that's my own bias. I've been to one too many conferences with one too many talks about proteins. In all seriousness, the idea of protein receptors is one of the most important in biochemistry. For a long time it was known that hormones had an effect on cells, but not understood how. Receptors are something that is almost taken for granted in most college level courses.
Congratulations to all the winners. There are other prizes that have or will be awarded (literature, economics, peace) but we'll leave that for some other blog to care about.
If you want to ask a question or leave a comment, head on over to the under the comments for this post.
Notes
[1] The other important difference is the science Nobel prizes are generally not given until long periods of time have passed and the contribution as been verified. The peace prize does not have the same requirement. In fact, it is often given within the same year of an accomplishment (see, for example, Barack Obama, Al Gore, etc.)