We bought lanyards a few trips ago to hold some of our "stuff." We purchased the clear pockets that TiggMan mentioned--I think they were about 3.5 x 5". In them we could put our park pass, room key, driver's license, a couple bucks cash, and sometimes we even carried little mini park maps that we printed at home so that we didn't have to deal with those big folding deals they give you at the park.
IMO, the lanyards worked great. We didn't have to dig in wallets, purses or fanny packs to put our hands on those important items.
The last trip we took was just my wife and myself, so we figured we didn't need to be as organized and left the lanyards at home. By the second day of the trip, we vowed to make them a permanent fixture from now on.