Yes, with some qualifications...
You can for example speak your search term into Google Search, and if you are an English speaker with good diction, it does fairly well. I am not sure about other languages.
If you are typing into an input area, and the keypad you are using has a microphone button, you can press it, and say your intended text, and again, if you are an English speaker with good diction, it will enter that text into the input area. For example, I downloaded a Note program from the Market called ColorNote. With it, I can select the microphone button and dictate a note to myself.
Don't expect 100% accuracy, but it can do a fair job.