Actually, halfway through SICP sounds like a great place to start projects that are interesting. For example, my first real exposure to Lisp was through Arc.

Actually, halfway through SICP sounds like a great place to start projects that are interesting. For example, my first real exposure to Lisp was through Arc. The tutorial was enough for me to write a basic ray tracer (I submitted it to the unofficial arc repository a few months back). I've never looked for open source lisp projects myself, but I'd give a site like github a try (just search for Lisp).