diracLE~ is a high quality realtime timestretching and pitchshifting external.
It is based on the DIRAC LE algorithm by DSP Dimension. It can playback from a buffer~ with no latency, in streaming mode there is quite some latency though.
There are some limitations: the samplerate should be 44.1kHz or 48kHz and smooth parameter transitions are not possible. It can function in stereo, but the channels are not linked internally, so they can have slight offset.
The zip file contains besides the external and a helpfile also 3 Max for Live devices which illustrate what you can do with it.
(note: it is currently Mac only)
update: the object is now max 6 ready, it uses 64 bit precision in max 6 (and still works fine in 32 bit mode in max 5)