Shaila,
You can very well use Spring framework with portlets (I am doing so right now). Your question needs to be more specific though. In general I can tell you the following:
1. Go to springframework.org to get details about the framework
2. There are a few intro to spring articles
http://www.springframework.org/documentation 3. Arguably spring framework can do pretty much everything a commonly seen
J2EE application running inside a container can do. This includes remoting, transactions, working with such framework as Hibernate to do persistance, working with struts/JSF to handle presentation layer and more
If you list your specific requirements, I might be able to help you more. What are you using? WebSphere Portal?