Soldering leads/pins to SMD/SMT for solderless breadboard prototyping?

When you say bread board, I'm assuming you mean solderless bread boards.

Soldering legs to individual SMD caps will be fairly difficult, and likely fragile. You should be able to buy through-hole caps that have sufficient voltage at RadioShack, or at just about any online electronics distributor (digikey, mouser, etc). Here is an example of a 50V through hole capacitor.

When I want to use SMD components on a breadboard, I usually attach them to a breakout board first, and then run wires or header pins from the breakout board. Bellin makes many different snap-out breakout boards like this. It's a little on the pricey side, though. You could make your own by cutting up some solder-type bread boards. SchmartBoard is another brand of adapters you could check out.

Just thought I'd share since I found exactly what you were looking for: SMD to Breadboard Adapter Boards However, they are only meant to work with 0805, 0603, 0402 sized passives (although I'm sure it wouldn't be too difficult to make 1206's fit).

A better solution may be breakout boards also called Surfboards (get it, breakout boards for surf-ace mount) from Capital Advanced, Digi-Key, and others. The 6000 series is for discretes, and the 9000 series for ICs.