I'm not sure if there's that type of speed dial but you can place shortcuts for contacts on your home screens. The default launcher has it built in, HTC Sense has a beautiful implementation of it, which can also be had by buying LauncherPro Plus.
Using the default speed dial utility I can not set one of the speed dials if I search my contacts. If I scroll through my list I can select a contact and it works. With 300 contacts this is a curious annoyance. any ideas? I am on a Droid X.