I'm going to start working on my own custom blogging platform in PHP. It's been something I've been wanting to do for a while; and something I perhaps should have embarked on sooner before attacking bigger stuff with a large coding shovel. WordPress is great software - but I want to be able to write my own AJAX post editing stuff, and I want total control over all of the code that powers my blog. I don't use half the options and functions that WordPress has available - and in my opinion that's memory and processing cycles wasted when my blog is loaded.
Not got a clue when it'll be finished, but I'll keep hacking away now and then until I've got something worth showing.