Goatboy wrote: Pick up a book by Forrest M. Mims on basic electronics.
Seconded. I actually have a workbook by him lying in my drawer. Easy to understand, and the projects inside are easily adaptable for exploration. The problem with RFID is range. It has a very small one, so you'd need something else to sense it's presence and then inform you of it via another means. The tag itself won't actually be able to transmit it's location in GPS coordinates to a remote server, if that's the kind of thing you were thinking of doing. That'd be very cool, but unrealistic.
You could build a really minimalistic computer that runs Linux and transmits the information every time it can get access to a wifi hotspot. I've seen really small boards sold and advertised as capable of running Linux, though the technical skill required to get it all working (not to mention adding WiFi capability) would be quite high.