With Froyo (Android 2.2) on the Samsung Captivate, I finally got voice-dialing working, though it took a bit of work.
1) Install TopVoiceControl
2) Install TTS Extended Service 3.1
http://code.google.com/p/eyes-free/downloads/detail?name=tts_3.1_market.apk&can=2&q=
At this point, I am able to...