1- Dragon Dictation Free
This is a free voice recognition app that lets users easily speak and instantly see the text or email messages. It is believed to be 5 times quicker than typing on the keyboard.
2- Speech Notes
This is a note taking app that allows users to turn speech into text via the help of internet connection. Just click on the Mic button once for speaking and the second for transcription.
3- TalkBox Voice Messenger
This is mainly for sending text messages with a combined voice and text input.
4- Vlingo-Voice App
Vlingo is like the Siri Assistant that some iPhones 3GS and 4 have. Just speak to it and you will get many things done. It even integrates with your twitter and Facebook accounts.
5- Google Voice Search
This is Google Search app for the iPhone and iPad. You can use it to search the web using your voice and no need for typing.It also provides quick access to other Google apps like Gmail, Calendar, and Docs.