It amazes me how something like a song that you haven't heard in a while can immediately bring back memories and past events as if you just experienced them yesterday. I heard a song yesterday and as soon as the first note played it took my breath away. I immediately recalled some things that happened a little while ago. I've read that taste (oddly enough) is the the strongest link to past memories, more so than even sight. I personally thought that smell would have been higher on the list, but I suspect that since smell is a part of taste that is the reason why taste ranked higher.
I think that deja vu is also an interesting phenomenon, but maybe that should be another whole thread?