Embedding webapps into other webapps

I've been tasked with figuring out how we can offer a few of our products in one 'container' of sorts, such that a customer can seamlessly navigate from one app to another, if they're signed up for both.

Now, we have some different technologies floating around. Our main app is a Rails app, and the one we're hoping to embed is a Spring MVC data service with SproutCore frontend (we'll call it Sofea).

The original suggestion was to incorporate Sofea frontend into the Rails app and by proxying data requests through to the SpringMVC app but I'm loath to do this as I think it adds complexity to the codebase and ties these two apps together which (in my opinion) should be maintained as separate apps.

So here's my question. Does anyone have experience with 'embedding' an app through an iframe. I'm looking to allow a user to click another link and have their session data propagated through the iframe to allow them just to load up and be logged into this separate app being none the wiser that it is in fact being loaded through the iframe.

Can someone point me to some setups that might开发者_开发问答 be doing this type of thing and maybe some docs describing how it works? Or even let me know if there are any issues with such a setup. I've never done this before, but I'm pretty sure people do (like FB apps ???)