There are also text to speech freeware progs that will save to .wav / mp3 or wma format.

I have used Text to Wave and it can be found here:

http://smart-butler.com/download.html#text2wav

It's free for personal use.

Microsoft Anna is probably the best voice you'll get from it.

You can't beat the real thing but if you are pressed for time or don't have a good soundcard or microphone or just plain shy, then it's a good option.