Julie Meloni is the author of the forthcoming Blogger in a Snap, which promises hints, tips, tricks & a few add-ons / extensions. Looks good!! Congrats on being almost done with the book!! I'll check it out in a month or two!! Would you be interested in having a co-author for a sequel of blogger hacks & add-ons?
(well, if you don't ask.....)
My book is aimed at the real beginners of the world, those getting into blogging, those who blog but are terrified of html and things like that, those wondering about that "feed" thing and why they need one, etc. REALLY beginner stuff, and I daresay the "tips and tricks and add-ons" are not really what you or I would think about when we think about tips and tricks and add-ons. It's more like "so you want to add images to your blog? Ok!" not "how to get the most out of someone else's template language and make your blogger blog something truly interactive and what not."
If my book does well, which it should based on the niche I'm trying to fill and my track record with other books, then they'll want me to follow up. I would totally be into doing something together -- or I'd just help you propose your own darn book and help you get it through to approval, depending on how I felt that day about my workload. :)