I had good luck documenting my build using Blogger.com for my free WEB based Blog solution. However, I do pay a $10 per year registration fee so I can have my own WEB address for my builder's Blog.
The basic Blogger.com service is free and has storage up to 10 gig I believe ... I have tons of high res photos documenting my RV-12 build, so opted for additional storage which costs @2.99 per month which I feel is a fair amount for the service. I wanted to post lots of photos of the build with me in a large number of them so the FAA would not have any doubt I built more than 51% of the aircraft. If you don't post tons of high res photos, you could likely get by with the basic free storage.
One nice feature of Blogger.com is that there are many template formats to choose from making the time to get a Blog up and running quite quick. You can customize the look very easily once a format template has been chosen. You can easily customize the cover page using photos and also add tools such as search features so others can easily search your Blog based on a part number, assembly name or a tag name such as fuselage, wings, ect. Admittedly, there is a little bit of a learning curve to Blogger but once you play with it a little to get the feel for how it works it is easy to create posts documenting the building process.
Have a look at
http://www.dogaviation.com/ as an example of one of the Blogger templates I used.
Enjoy your build.