Two main types; Boeing favour the tracks-and-roller design, covered with "canoes", Douglas used the "hide-it-in-a-hinge" mechanism on the DC-9, DC-10, MD-11 etc. The Boeing mechanism seems to be predominant, judging by the number of airliner wings with canoes on the trailing edge.
Chris Brady's website on the 737 (The 737 Information Site) might be helpful, covers the 737 family in some detail. The NG has a double-slotted system, the 300 & 400 had triple-slotted. (
www.chris.brady.ukgateway.net)