Legatto string-skipping is a really cool exercise to warm-up your fretting hand, and more importantly, provides a great technique to implement in your tunes. If executed properly, string-skipping creates a very intervalic sound and is great for pentatonic stuff (And if you're feeling really ambitious, try alternate-picking string-skipping. That's a challenge at high speeds).
Here's a string-skipping lick in E:
E |---------------------------------p-7-h-10-h-12----------
B |--------------------------------------------------------
G |-----------------p-7-h-9-h-12---------------------------
D |--------------------------------------------------------
A |-p-7-h-10 h-12------------------------------------------
E |--------------------------------------------------------
Try descending as well. If you really want a challenge, try a diminished (ie. using wide-fretted intervals ;)) string-skipping riff with alternate picking.
That'll keep your fingers busy. Use a metronome.