I just got my Archaeology magazine in the snail mail, and in this issue (January 2008) they have the top ten archaeological discoveries of 2007.  There's also an expanded online version which can be found here:

http://www.archaeology.org/0801/topten/

My favorite among these discoveries is probably the Polynesian chicken bone found in Chile.  DNA studies of chicken remains dated to 1321 to 1407 show them to be related to chicken from Tonga and Samoa, thus giving strong evidence the Polynesians made it all the way to South America centuries before the Spanish showed up. 

The Solar Observatory in Chankillo and the early squash seeds, both of which found in Peru, are really interesting albeit in two extremes of the scale.  The solar observatory was a thing of magnificence, meant to show off the ruler's power over the natural world. On the other end, the squash seeds are as mundane and humble as it gets, but its dating to 10,000 to 12,000 years pushed the age of agriculture in the New World pretty and bringing it contemporaneous with the Old World. 

On the other hand, the discovery of Lismullin Henge in Ireland carries a somber note.  It is a large Iron Age ceremonial enclosure a mile from the legendary Hill of Tara, no doubt connected in some way with Ireland's ancient capital and religious center. Unfortunately it was unearthed as part of the construction of the new M3 highway, and it is planned to be destroyed and paved over for the new motorway. Conservancy groups and politicians are fighting this project, but it's far from certain if Lismullin will survive. 

What are your favorites?