What the heck do you call that?!?
LEGO has made an amazing number of different pieces over the years, and rarely if ever does the company give an official label to each piece. So how do fans keep them straight? While I'm not sure there is a single "official" standard name list, there are at least two places on-line to look up a "reasonable" name for a piece: Peeron and Bricklink. Peeron is a searchable inventory of many (5000+ at last count) of the sets LEGO has made over the years: search for the set you have, and find out how many of each piece it has (and what color; currently it lists something like 10,737 different pieces). Bricklink is a marketplace of LEGO resellers, and list 13,148 different parts in its catalog tree. These two don't always agree, and there are other naming conventions, but these are two reasonable places to go to find the name of that "thingamajig from that old whatsitsname set I got back in 1980something".