Deploy to different environments using Eclipse

This page describes how to deploy with Eclipse or the Force.com IDE: http://wiki.developerforce.com/page/Deploy_Force.com_Applications_Faster

And this page describes the development life cycle: http://www.salesforce.com/us/developer/docs/dev_lifecycle/salesforce_development_lifecycle.pdf

Another resource if you want to deploy metadata via the Force.com Migration Tool: http://www.salesforce.com/us/developer/docs/daas/index.htm

In addition to the above a not well known feature is, that in a eclipse project you can select multiple files using CTRL, then right click on one of the selected resources and select "Force.com/Deploy to server..." in the context menu. That way you will deploy the subselection only, and will not be bothered with a huge list of classes/pages/etc that you have to search for the right files.

hth