Time Magazine lists down the Top 10 scientific discoveries of 2007. Among them are:

1. Stem Cell Breakthroughs
2. Human Mapped (J. Craig Venter's genetic sequence)
3. Brightest Supernova Recorded
4. Hundreds of New Species discovered in in the Weddell Sea off Antarctica, Suriname, India, Uganda, Madagascar, Sumatra and Borneo, and Taiwan.
5. Building a Human Heart Valve from bone marrow stem cells
6. "Hot Jupiters" Discovered
7. A Big Birdlike Dinosaur
8. Man's Migration Out of Africa
9. The World's Oldest Animal, a 405 year-old clam
10. Real-Life Kryptonite unearthed from Serbia

Read the feature article here. Also see the related article, Top 10 Medical Breakthroughs.