Patek Philippe developped three base movements for almost all of its current collections. (with the expection of some lady models, some extremely high-end models and of course quartz models.)
The cal. 215 is the most simple and reliable one. The hand-winding models of Calatrava line and the Gondolo line are equipped with 215. Typical models with cal. 215: 3919, 5115, 5117, 5119, 5196, 5109, etc.
The cal. 240 is a super-thin automatic movement developped in the 1970s. Most Patek perpetual calendars are equipped with this beautiful movement. Some simple automatic Calatravas are also equipped with 240. Watches with cal. 240 have either small second hands or no second hand. Typical watch models: 5026, 5000, 6000, 5120, 3940, 5110, 5130, etc.
The cal. 315 is another popular automatic movement. Althouth there has been critics on its reliability, the cal. 315 is still widely applied to Calatravas, annual calendars and perpetual calendars. Watches with cal. 315 have normally big second hands. Typical watch models: 5027, 5127, 5035, 5036, 5146, 5050, etc.
The newly (I guess in 2004) developped cal. 324 is a, technically speaking, modification of the cal. 315. Among the new specifications, ceramic ball-bearing, the newly designed balance wheel and an increase of frequence from 21,600 to 28,800 are the most significant highlights. Typical models with cal. 324: 5296, 5396, 5135, etc.