A very nice feature of login process of InfoQ.com and ICEfaces.org is the end users don't have to leave their current page in order to login, instead of that, a small balloon is shown and the user provides his credentials.
If the login is successful, parts of the page is shown.
I'm trying to do the same thing with Seam application.
RichFaces has modal dialog component which looks a perfect fit for this situation.
Do you think that I need extra things to take into account?
seamframework.org has a similar feature. Take a look at the wiki example on which it is based to see how it is implemented.