Can someone give me a good idea of what the differences are of all these Primes?
Hmmm... Okay, quick rundown... the three pancake lenses are the Lumix 14mm f/2.5, m.Zuiko 17mm f/2.8, and Lumix 20mm f/1.7. These lenses are super-slim, which normally means that you can't expect faster than f/1.7 on these lenses (ie, the Lumix 20mm is the fastest) and they may not be quite as high quality as faster lenses... but still much better than what you could get from a zoom lens of similar build quality. You probably won't need more than one such lens, and of these three the Lumix 20mm f/1.7 is the most popular.
For non-panackes in that middle range, you have the choice of the Voigtlander 25mm f/0.95 Nokton and the Leica 25mm f/1.4 Summilux. Both are more expensive but very high quality lenses. The Leica is Autofocus capable, but the Voigtlander is manual focus only. The Nokton of course is as fast a lens as you will ever find (it is the cheaper version of the Leica Noctilux, but the Noctilux is not available in Micro Four-Thirds mount).
For a longer focal length (great for portraits), you have a choice of either the faster general-purpose m.Zuiko 45mm f/1.8 or the slower but macro capable Leica 45mm f/2.8 Macro-Elmarit.
For wide angle you have the high grade m.Zuiko 12mm f/2 for a "normal" wide angle, or you have two choices for ultra-wide fisheye lenses, the Samyang 7.5mm f/3.5 fisheye or the Lumix 8mm f/3.5 Fisheye. Of course, fisheye lenses are very purpose-specific.
Unfortunately, there are no non-fisheye ultra-wides or telephoto prime lenses yet for the Micro Four-Thirds mount. If you want an ultra-wide, you can either use adapted lenses or zoom lenses. For the ultra-wide angle there is the very nice Lumix 7-14mm f/4, and the cheaper m.Zuiko 9-18mm f/4-5.6. If budget allows, the Lumix is the better lens.
For telephoto there are only slow zooms such as the Lumix 100-300mm or m.Zuiko 75-300mm. I can't tell you much about them, as I have no personal interest in slow lenses.
If you want anything faster, there are lots of options available in adapted lenses - for both prime and zoom lenses.
