There are many products on the market. Some might be expensive. FTFT offers an overview of two free tools: Chrome app Dictanote Speech Recognizer and Dictation.io. The latter is pretty handy!
Try them out and judge for yourself.
Some of the tools presented by the latest Edutopia issue might be more applicable for younger students, but some (e.g., myBrainshark, PosterMyWall, and Screen-o-Matic) are applicable to any audience and presentations in classes or conferences. Check them out!
There are some commercial packages available on the market. However, if you just would like to try the tools and/or add accessibility to your website (or blog?) check out these three tools: Speak It, Announcify, and Select and Speak.
More details are available at FT4T.