Here's a simple, yet brilliant tool for organizing a crowded camera bag - LenzBuddy Caps
While the LenzBuddy body caps
are more novel than [in my opinion] terribly useful (but who doesn't like bling?), I can see where their lens end caps
could help you easily distinguish which lens is in which pocket at a glance.
Of course, a roll of duct tape and a magic marker could accomplish the same thing, but it wouldn't look nearly as nice. ;-)