This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Strictly, one servlet does not have the ability to "load" or "unload" another. However, I'm not sure that "load" and "unload" are actually what you need anyway. I've never yet met an application that needed to do this sort of thing - there has always been a "standards compliant" way of achieving the desired result without messing with loading classes. Can you explain a bit more about what you want the behaviour of your application to be bothe befor and after the point where you plan to you "load" or "unload" a servlet?