Total posts : 45366
For free, you can enter short phrases into these three web pages and select various voices.
For inexpensive software, TextAloud is pretty good: http://www.nextup.com/.
Nextup also sells several voices. However, if you want NeoSpeech Kate and Paul, you can get them cheaper here: http://www.smarthome.com/12662.html
I use a synthesised voice for time announcements in ZaraRadio, but personally, I wouldn’t use it for regular announcements.
Edit: You can also get TTS voices from Loquendo, Scansoft (or whatever they are calling themselves this week) and others.
In my opinion, the AT&T and NeoSpeech voices are the best sounding of any I have heard. The NeoSpeech voices sound more natural, but the AT&T voices are slightly better with some pronounciations.
For a free program that is similar to TextAloud, DSpeech is pretty good. I think TextAlound does a better job, though.