[plt-scheme] where to begin

Hello everyone,
I'm an undergrad. I have learning to do, and would like to get on  
with it.

I want to get into the more esoteric side of scheme, and hopefully  
strengthen my knowledge of current programming language research.  
I've got the Lambda the Ultimate blog in my feed reader, but most of  
the stuff is over my head. Coq and provability have been know to  
cause my eyes to glaze over for 20+ minutes.

I thought I might port some of my current ruby code into scheme to  
fiddle with any new techniques I find. It's a Genetic Programming  
framework, but that's irrelevant, I just want a decent sized project  
to see the effects of. I'm open to alternate projects so long as I  
can wrap my head around them.

I'm looking forward to trying contracts and laziness, but am not sure  
what else to play with. Anything else I should investigate?

Joseph Holsten