One of the most hyped features of recently launched iPhone 4S was Siri, the new voice assistant application for iPhone. I don't own an iPhone 4S and hence I can't comment on how good Siri works. But upon searching a bit, I found out that there are quite a few good Siri alternatives for Android readily available in the Android Market and most of them are free too. Here is quick collection of top free Siri alternatives for Android.
Vlingo Virtual Assistant is perhaps one of the best voice-powered Virtual Assistant on Android. I was pleasantly surprised with the quality of this app, both look-wise and the way it worked. From sending texts and emails to updating your Facebook/Twitter status to checking in with Foursquare, Vlingo does almost everything it is asked to effortlessly.
Speaktoit Assistant app is yet another Siri alternative for Android that just works. With the image, name and everything, Speaktoit Assistant gives you an impression of something that is real. You can ask Jane anything under the sun and you get answers right away. Speaktoit Assistant answer questions, find information, launch apps and connect you with various web services, such as Google, Facebook, Twitter, Foursquare, and many others.
Skyvi is perhaps the application that I spend most time with among other Siri alternatives. All these voice assistant are not perfect. Mistakes often happen like you see in my screenshot above. But you will have a lot of fun for sure.
Iris is siri in reverse, yet another attempt to replicate or better the voice assistant application for iPhone called Siri. Does everything what you expect it to like making calls, searching the web, texting and so on. Iris even boasts of Android 4.0 Ice Cream Sandwich inspired UI.
AQ for Droid is the least rated application among the lot, though the screenshots and video looks pretty nice to me. Developer claims to have already been working on all the shortcomings, so expect an upgraded release of AQ for Droid very soon. I haven't tried it myself yet. You might want to give it shot anyway.