If you are into live looping devices Sooperlooper is so much fun. Really useful for jamming and "scrathpad" creativity. It runs under the JACK-low-latency-audio server. Only available for OSX and Linux though.
I had so much fun with this! MIDI-mappable controls (as well as computer keyboard). Check it out:
"SooperLooper is a live looping sampler capable of immediate loop recording, overdubbing, multiplying, reversing and more. It allows for multiple simultaneous multi-channel loops limited only by your computer's available memory."
I tested it on both Mac and Linux. It was a while ago, so I don't remember exactly - but it was easy to install jack in OSX. But I remember I used Soundflower also, as to software patch the Sooperlooper output to Audacity. This so I could do live mixes/mix-downs on the fly to Audacity.
i advise you use jack or run it as an audiounit plugin. I used to run it as an audiounit in Mainstage. Soundflower is sorta broken at this point and often will eventually after (depending on how you set it up) a few minutes or half an hour, start to have clock sync problems and make horrible sounding audio. Just a warning :)
My experience was that sooperlooper, while awesome, would occasionally do unexpected things in performance as a audiounit, like undo would mess up a loop sometimes or a click or pop would appear in the loops randomly when overdubbing making the whole piece sound sorta bad from then on.
I'm currently working on my own looper system in MaxMSP - not ready for sharing yet, but I've been performing with it. It has most of the features of sooperlooper so far pretty much working, and a bunch of features that sooperlooper doesn't have - like it is totally non-destructive, shows waveforms and allows visual cropping of loops, and has global presets so you can save the state of a piece as you're performing and hit a button to go back to that state at any time (ie you can make an A section and a B section etc etc and switch back and forth between them live). If i remember, i'll post here when i get to a place where I could share it (ie I need to make the MIDI control mapping generic rather than hard-coded to my foot pedal…).
@arvidtip: nice! this sounds interesting! I am not a programmer - so which platform is it for? Is it also stand-alone or plug-in? What about audio drivers? Do I need a dedicated soundcard? Latency? It was a while since I fiddled around in the audio department - my focus on video production. I have an old mAudio delta44 but I think it's Win only. When I did audio on Linux I ran a low latency RT kernel and the latency was very low. Thanks!
edit: If i remember there was a driver in Ubuntu Studio for the delta boards. At least some sort of control surface. And yes, Sooperlooper had some minor bugs. I think he did some bug fixes a couple months ago.