We've got two of these http://www.petsathome.com/shop/dog-play-pen-by-pets-at-home-25507 around our patio, for bunny free ranging!
There are pros and cons to the drop pin type.
On one hand they stop buns from lifting the pen up if the pins are stuck in the ground, and you can attach more panels really easily.
On the other hand, they're really difficult to move around the garden because the pins stick in the grass and end up getting bent.
TBH I find it easier to just cable tie the panels together
I have drop-pin ones! These ones:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120562416182
I have a 76cm one and a 61cm one and use them indoors as a mini run and also to fence off the TV area and the PC desk and when it's dark, the curtains! They're good because you can separate them and connect them up so you can use as many or as few panels as you want.