Lenses on the Olympus E-m5
To follow up a little bit, almost any other SLR lens can be mounted on an m43 camera with an adapter, as well as 4/3 lenses, C-mount lenses, and rangefinder lenses. However, only the 4/3 lenses will auto-focus, and not that speedily at that.
Given the number of relatively cheap native lenses, I'd be hard-pressed to recommend adapted lenses to a beginner. Beyond the kit lenses (which are surprisingly good), you can get the Panny 14mm, or the Sigma 19 or 30mm--all for under $200 US. By the time you've added the cost of an adapter (about $25 US) the legacy lenses aren't all that much cheaper.