A 2s1p is just a 2s pack ie 2 cells in series to give you 7.4v at what ever the mah rating is on the pack. If it is rated at 2200mah then each cell is rated at 2200mah.

A 2s2p pack like this...

[link]http://www.hobbyking.com/hobbyking/store/__18605__ZIPPY_Flightmax_5400mah_2S2P_35C_Hardcase _Car_Lipoly.html[/link]

is made up of two sets of 2s cells in parallel. But each cell is only rated at half the total pack mah.
That is to say, there is a 2s 2700mah pair of cells connected in parallel with another 2s 2700mah pair of cells...2s2p 5400mah.

I think I've even confused myself. But that's it.