With the anticipated 3G release date of June 9th, the iPhone may be the next producer weapon of choice. Roventskij has just released the IR-909 1.0 Beta 2 version of their drum machine for a donation of "a dollar or two." The IR-909 comes complete with a 16 step sequencer, 4 patterns, and 8 drum sounds.
Also available at the website is the iPhoneSynth, which includes a 16 step sequencer and the ability to change lenth and oscillator type for each step. Low pass filter is even included!
Find out more about the IR-909 drum machine and iPhoneSynth