NetTUTS have put up a great post on speeding up a website, but you could easily translate that into speeding up your WordPress blog. While these might not increase your speed like caching or anything else like that, it is still a very useful guide for compressing images, CSS, and finding errors.
We’ve talked about compressing CSS before on Blogging Pro in a post entitled, CSS Optimization: Make Your Sites Load Faster for Free.
I am really interested in the the section on using libraries and frameworks as I’ve been hearing more and more about people using them to speed up their development time, or require less code, through use of libraries written by other people.
If you are interested in speeding up your blog, or the theme you are going to release, I’d recommend checking out the post on NetTuts.