Having learnt scheme should now put you in a unique position where you can identify syntactic sugar and the key features of a language rather well.
Scheme is useful, but if you are looking at larger programs, you should probably have a look at Common Lisp. Though it is not that "clean" and "academic" as Scheme, it is far more powerful. (http://gigamonkeys.com/book/ is a good reference)
Then again, you could go and learn a strongly typed functional language, like Haskell or OCaml. OCaml is particularly good for writing desktop applications.
If you do want to stick with Scheme, like Macnell suggested, I would suggest you to pick up Racket. It is easier to get things done with that MIT scheme.
Finally, you could (and probably should) learn Python. It is probably the easiest language out there to pick up, and has wonderful libraries that make most tasks easy. You can write your own email client, or a program to fetch you lyrics, or any of those nice little first-desktop-apps. "Dive Into Python" by Mark Pilgrim is a great source.