Habitual Foursquare users don't have much context for their check-ins -- it's easy for them to track their favorite haunts, but not their long-term trends. The just-launched Foursquare Time Machine could help draw those missing connections, however. Sign in and it creates a map-based timeline of each and every check-in, color-coded by its nature. While the superficial result is a very pretty light cluster, it's surprisingly functional underneath: members can see their exact check-in times, their favorite days of the week and their most active periods. Naturally, there's also an option to share the stats with others. Time Machine is already popular enough that it's struggling to cope with the early demand, but the functioning site should be worth visiting for the (eventual) trip down memory lane.