A summary of lenses available in M4/3 mount.
The old list always needed attention so has been abandoned.
The official lens list with details is at http://www.four-thirds.org/en/microft/lense.html
A useful M4/3 lens list with info on 4/3 lenses http://hazeghi.org/mft-lenses.html
Another excellent list is at http://hennigarts.com/micro-four-thirds-lenses.html
A newer list on the scene at http://www.m43lenses.com/
Some of the Panasonic lenses have the Leica name on them and are higher quality but naturally have higher prices.
Be aware that Panasonic switched OIS lenses allow the choice of in-lens or in-body stabilisation when on an Olympus body.
The unswitched OIS lenses currently default to no OIS available when on early Olympus bodies and E-M5, the first bodies to allow lens unswitched OIS to function are E-PL5 and E-PM2 announced in September 2012.
The newer Power OIS works better than the more commonly seen Mega OIS in the Panasonic lenses.
Some Olympus bodies will do Sync-IS when the Olympus OIS lenses are attached, see the timeline for that.
The older 4/3 series of lenses can be adapted to the M4/3 bodies but focus is slow, the E-M1 body has added phase detect AF to help with the older 4/3 lenses and make their AF faster.