I'm a big fan of Brian's, aka Aleph Null's, circuit designs he's been kind enough to share over on the MadBean forum. Here's one of his latest offerings, the Special Sauce. In his own words, "It's a short delay with envelop control pitch bending. This makes for unique chorus, doubling, slap back, and vibrato effects." More info here.
This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.