Hitchhikers
Hitchhikers are trackable items that you can move from cache to cache. An example of this is a candle that has traveled from Australia to Arizona, and a Mr. Potato head that leaps from cache to cache. For example you can purchase a Groundspeak Travel Bug, which is a tag that you can attach to an item so you can track its movements through the web site.
There are two main types of hitchhikers, Travel Bugs and Geocoins.
Travel Bugs
Travel Bugs are items that are placed in a cache with a tag or a note asking to move it from place to place. Travel Bugs many times have a goal to get to a certain destination or to visit certain states or countries.
Players can discover a Travel Bug that's in a cache that they find, or they can retrive the Travel Bug and drop it into another cache to help the bug meet its goal.
Geocoins
Unlike Travel Bugs, which can be anything you'd like, Geocoins are simply coins. However, there are many different types of Geocoins, many have their own logo on Geocaching.com.
Some people even have collections of their own personal Geocoins that aren't placed in caches, but are brought to events so that cachers can share their stories and allow other players to discover them. Coins are available many different places. I plan to try to get a collection of coin sites that I like together so that I can share. Also, anyone who can afford it can get a coin minted. They can create a personal geocoin, or a coin for an event, or even a coin for a group of people. Creativity is the limit here.
My Collection
Here is my personal collection:
Jennie's oneyedjack Geocoin: I purchased this from a fellow cacher at our monthly breakfast. It was the first personal coin that I had seen available to purchase, so I figured it would be a good way to start my coin collection. I would like to purchase coins from all of my geo friends, if they make coins available.
Jennie's Backwoods Geocoin: For the 2007 Wichita River Festival, a geocaching event was added (more info on that soon), and I was asked to help create some clues for our puzzle cache. As payment for helping out, Backwoods gave me a geocoin that was created to commemorate the event. There are plans to recreate the event in 2008, and I hope that they can create a coin for every year.
Jennie's Kansas 2006 Geocoin: I purchased this to commemorate my beginnings in geocaching. Originally, I though of buying a coin for every state that I find a cache in (every year), but I figure that might be a tall order. For now, I started caching in 2006, and I found my first cache (my first many caches) in Kansas.