I am doing similar research, not only for my MA,,, but also for my school district. If you would like to see what i have for my Literature Review, iw ouldn't mind sharing. :) Crazy to see that some other people have completed research on this topic or are starting research on this topic. Makes me feel much better about it. If you look in my topics that I started, I have a few links to different researchers that have done this.
I'll second Julia Osteen's plugs for BlogMeister. I have considered other blogging platforms but the community of users that I have gotten to know through BlogMeister and its related Yahoo discussion group keeps me coming back. There are sometimes bugs and quirks but for the most part it is more stable than other popular and free educational blogging sites. And I have tested many of them with kids! Some people don't like the fact that you can't customize it all too much but I actually like that aspect. I'd rather have my students stand out for the work they post rather than the colors, widgets, fonts, or backgrounds they use. I also have a thing for consistent navigation across our whole class. . . .
It seems like you might have two questions here: How to start? and What research is out there to support blogging in schools. The thread Lucas started and refers to here will give you a lot of info on the research end.
The one tip I would give about starting is to make connections RIGHT AWAY for your students. I have found that if I find a class that is blogging and has it set up so each student has a "page," I simply assign each student to each one of my students and have my class comment. I know how important it is for each student to get a comment so I make sure to do it this way first. Inevitably the class comments back. And then we're off! Sometimes some classes comment more and the relationship builds from there. Sometimes the relationship builds into more than just "drive-by" commenting. But sometimes the drive-by commenting is all that we can commit to for the time.
From there you can delve more deeply into "good" commenting, etc. From there, you can question the desire to make across-the-county (or world) connections or whether it's better to focus on local (among your own class or grade) connections.
But you have to start those connections right away. Very quickly the kids will lose interest if no one comments to them, if there is no tangible audience for them.