http://io9.com/5287267/r2+d2-spotted-hiding-in-star-trek-movie
Heres more easter eggs...
http://trekmovie.com/2009/06/11/location-of-r2-d2-easter-egg-revealed-more-star-trek-easter-eggs/
Google is great for looking stuff up.
John Knoll, ILM visual effects supervisor, worked on the effects for Star Trek First Contact and the Star Wars special editions. He slipped the newly made digital model of the Millenium Falcon into the Borg/Starfleet space battle. This was reported in several Star Trek fan magazines and can be seen if you have a DVD player with zoom and slow motion features.
The ship is quite small and is flying typically above and behind the Borg cube in several shots of the battle. If you can zoom and slow motion your DVD image, you can make out the shape of Han Solo's ship.