Just as we're reaching the last day to buy Korg's app for 50%-off, two more deals have surfaced!
finger's MoDrum is down to $4, leading up to the release of the next patch. This drum machine, from the makers of BassLine, has a solid Virtual MIDI implementation with both Notes and Sync. Development and support have been top-notch on this one! Unlike most of the drum machines out there, this one is all synthesis!
Additionally TB MIDI Stuff is now 50%-off, down to $5, for even more MIDI goodness. This sale brings it down to TouchOSC's price-point, and for that price I think it is definitely worth while if you want to make your own MIDI interfaces. This is unique from TouchOSC and Lemur, as you can edit your layouts right on the iPad.