Create actions to take care of the re sizing.
I created 4 actions all told.
I save at full size for my records but I also save at:
800 x 600 both portrait and landscape orientation 150dpi - for posting here mainly and on my flickr
600 x 480 both portrait and landscape for ephotozine - 72dpi
This covers all my posting needs and email needs, the 800 x 600 should be fine for emailing as well.
The beauty is that when I've finished processing my pics I can then use automate/batch and then select the resize action I need, choose the folder to save in and its all done automatically in seconds.