Manufacturer: Vulpus Labs
FREE
A bank of eight attenuvertors and DC biasers for signals of all kinds. Use the "add" knob to add voltage to (or subtract it from) an input signal, and the "mul" knob to attenuate/invert it.
It's not fancy, but it solves a problem I kept having - wanting control of the range of the LFO or envelope signal I was modulating something with - and it's free.