Have a look at:-
the "buying an aircraft" thread here, which has some info on groups
the "Group Flying" forum on the Flyer website
articles in the mags recently (currently one in Flyer (edit: Pilot not Flyer) about the contractual aspects of group operation, one a year or so ago about "172 in a group" flying).
[This message has been edited by FNG (edited 19 January 2001).]