A great looking app.

I use the babel package built into emacs' org-mode. It's not for everyone though.

It's worth investing in a tool like this. I find the act of keeping a journal to be invaluable to developing my skills as a programmer. I find it serves two primary purposes. It first provides me a historical record of how my thinking has been changed and influenced. And it helps me to recall difficult subject matter in deep, complex domains. I tend to have limited brain capacity so it's nice to have a "database" of my thoughts to lean on.