Best Android Voice Assistants
Android has a lot of apps similar to Apple's Siri. Here are some of those apps:
Evi - This is what I use. its fast and the voice recognition is excellent. It can only do basic searches though.
Utter - This is a new app and is featured pack. At its stage (its still on beta) its voice recognition is excellent, and if given root access, it can open apps for you with a voice command
Google Voice - Compared to Evi and utter, the app is FAST!! I would say that this could be because it's meant to work with an Android system but people say that even the iPhone version works great.
Other runner ups: Vlingo, Skivy and Speaktoit