Keeping Track of Web 2.0
I'm not sure this will help you keep them straight, but you might discover something new and helpful.
Go2Web20.net is a directory of web 2.0 applications and services. The home page displays a screen full of logos for different applications. In the mood to play? Just scroll up or down with the little purple arrows, and click on what moves you.
If you're looking for a specific application type, you can either search or browse the tag cloud (click on "Select Tag"). Visually it's a lot to take in, but there's some pretty interesting web applications included here that you might not have found otherwise.