The mechanic has a real elegance to it, so, I decided I wanted to use Target 20 for saving throws as well. Delta has his own system and it looks good, but I wanted something a little different.
I wanted a similar baseline for all saves with about a 25% chance of success. I typically make traps/poison/etc. harder by tacking on a -2 or -4 when necessary. That's just my DM style.
I wanted the races (elf/dwarf/halfling) to maintain their save edges. I wanted the monk to be a bit different than the thief. I wanted the paladin to get his +2 to all saves back.
This system is somewhat transparent to the players -- they really only record their single save AND any relevant bonuses. The categories are for my reference only. I've recently developed a renewed appreciation for the "Saving Throw Pentaverate" thanks to Hack and Slash.
So, here's my table. YMMV.
The Base Save Bonus is based upon the character's level. The maximum bonus is identified as well. A roll of 1 on the d20 fails. ALWAYS.