This logic probe design was featured on Hackaday.com blog, and I was interested in assembling a couple of those. So, I made a quick KiCad board that'd be as small as possible - and in the end, it's very very small, using SMD components - but still hand-solderable =) I figure that if you'll want to use this probe on 3.3V designs, you'll want to use a 3.3V-compatible version of 555 IC.
UPDATE: Got the PCBs - 20 of them! Haven't tested them yet, but will do soon. Will send them out to Europe for cost of postage.