You need OM-type zuiko lenses for any of the OM cameras.
The lenses made these days for the 4/3 cameras won't work.
The OM zuiko's are very good and readily available on auction sites or secondhand dealers like KEH. Some third party glass is also available for the OM-mount and I think that some of these lenses are also quite good.
Olympus OM Zuiko and any number of third party lenses. To save yourself, time, money and aggravation, if you are looking for third party lens, stick with Tamron SP adaptall lenses and Tokina AT-X series lenses. Prime OM Zuiko glass that won't break the bank are 24mm f2.8, 28mm f3.5 or 2.8, 35mm f2.8, 50mm f1.8 (made in Japan version), 50mm f3.5 macro, 105mm f2.8, 135mm 3.5 or 2.8, 200mm f4 or f5. Vivitar macro focusing 2X teleconverter is nice. I've left one of my favorites the 85mm f2 off as it can be a little pricey. The Tamron SP 90mm f2.5 is nice as is the somewhat pricey 180mm f2.5. This should get you started. Want info on OM gear, you might check with the OM mailing list. http://lists.thomasclausen.net/mailman/listinfo/olympus. Bill Barber