Well, this isn't a great method, so hopefully someone else will come up with something a lot better ... but, here goes.
You can position the cursor at the beginning of the clip in several ways. Ctrl-Alt-arrows works well. Hold the shift key down and click on an empty spot on the timeline before or after the cursor (depending on which way you want to move the clip); exact placement not necessary. This will create a loop region. Under the lower right corner of the timeline are three timecode displays. The third one is the duration of the selection. Double-click this and type in the amount you want to move the clip by. This is in hh:mm:ss;ff format, so if the amount is more than 1 second you'll have to convert to that format. Hit enter. You'll now have a loop selection equal to the amount you want for shifting the clip. With snapping enabled, you can easily move the clip so that the beginning snaps to the other end of the selection area.
This sounds complicated, but it's actually a lot easier and faster than it looks.
I know about using the num pad to move clips 1 frame at time, but when yoiu need to move a clip 20 frames it would be nice to select the clip hit 20 on the num pad and the clip moves, the - key moves the clips backwards, other programs I use have this function, it would be nice if Vegas had this as well.
thanks
rod