I'm reading a book you might be interested in, called "[ame="http://www.amazon.ca/Talking-Hands-Language-Reveals-About/dp/0743247124"]Talking Hands: What Sign Language Reveals about the Mind[/ame]"
Thank you, Rebeccaj, for posting that link to the other thread... this is something I've thought about a lot as well. When I was taking ASL, my professor was not only CODA, but had a degree in linguistics... we talked a lot about how language impacts the way you see the world, the way you interact with it, and the way you process information. It makes sense that ASL-natives process information visually, approach problems from a top-down perspective, and tend to have better spacial skills.
What I find interesting is that when people use ASL, the part of the brain that processes language is active, but so are other parts that aren't involved with verbal languages. (I have my undergrad in Psych; I'm fascinated with this stuff... I'll try to keep from going off on a tangent 
The fact that ASL activates language centers in the brain is one of the things that supported the argument that ASL is, indeed, a full, vibrant language and not just English put to gestures. Also, small children go through the same phases when ASL is their native language (for example, kids will mix up you and me, or me and my)... I can still see my ASL prof "screaming" in ASL "ASL IS NOT ICONIC." (Which still goes through my head every time one of my hearing friends complains that a sign "doesn't make sense")
When my brain goes funny (I have seizures), I find that English goes out the window. I can't find words, and mix up words--like calling a chair a house. I've read things I've tried to write, and it all comes out in ASL order... But I can usually communicate just fine in ASL. One of my MRI's showed scar tissue over the left part of my brain that is connected with language--the Broca's area, and the dr's think that when things get wonky in my brain (highly technical explanation), that scar tissue makes it hard for electrical signals to go through that area.
If you read this article, it talks about those language areas of the brain, and about how that language loop is active in deaf people as well.
Rant over. 
