I didn't spend a whole lot of time on this, so there may be a faster and/or more effective way to accomplish the goal of separating workers to avoid the splash, but I have never seen it used so I thought it was worth posting (I apologise if it's already known). It is obviously inspired by the F1 worker split, and is fairly simple.
Here are the steps:
1) Select all of your workers (box them or ctrl-click)
2) Hit S (or whatever Stop is for your key setup)
3) Hold down F1 (select idle worker)
4) Right-click somewhere at the edge of your screen, but within your base
5) Right-click somewhere else at the edge of your screen (I think it's easiest to go around in a large circle on your screen. There may be better patterns)
Update: Shikyo has pointed out that you can perform all of the move commands while holding down F1; there's no need to press F1 repeatedly. This greatly simplifies things.
Keep clicking around your base until all of your workers have been moved. It can take a few seconds to do for a fully-saturated base, but the result is that your workers are all over the place and can't be splashed to death. It's also fairly hard to screw up as long as you hit S before hitting F1. Just keep holding down F1 and right-clicking around the screen.
As you can see, a Hellion would really only be able to hit 2 or 3 Probes at a time even if it was perfectly positioned, and it's quite easy to micro those Probes around without having to worry about the rest. It took me 6 in-game seconds to perform this with 20 Probes (ignore the timer on the screenshots), and that includes moving the screen to the base via the minimap.
You may be able to improve it by alternating the distance that the workers move so that the pattern is less of a circle and more of a checkerboard, but that's more complicated.
There is a potential issue with this technique, though: any idle workers you have will be moved as well. This is probably a benefit if you just have idle workers lying around for no reason, but it'll move any that you've deliberately positioned unless they're on Hold Position or are holding a Xel'Naga Watchtower. Edit: Thanks to Clamps for the correction.
CherubDown has been kind enough to create a video demonstrating how to perform the technique:
Jedimonky uses the technique at 7:40 of this replay: http://www.sc2replayed.com/replays/111208-1v1-terran-protoss-xelnaga-caverns