Oh my, this stuff is jammin (har, har)! I went back-n-forth between doing freezer jam, which sounded nice and practical, and traditional canning, which sounded dicey. Then, I read way too much on the internet on the subject and got confused. In the end, I did what I usually do and went with the more complicated ("dicey") method. It doesn't help that this is on my bucket list for the year 2012.
Anyway, in the end, a friend gave me some pointers and told me about Pomona Pectin (which I found at Whole Foods), and convinced me I could "rig" my regular pot and not have to buy a water bath canner just yet (although I will be adding one to my Amazon list very soon). For the record, I just used my steamer insert in the bottom of my stock pot in place of a canning rack (to keep the jars upright and from touching the bottom of the pot).
I got this great book for Christmas as well and used it to figure things out, although mostly I just used the instructions with the pectin for low-sugar jam. I de-seeded most, but not all, of the blackberries, by pureeing them in a small food processor and passing through a sieve. The remainder I just mashed and combined with the juice/pulp to give the jam a bit of chunkiness. I only had enough to make 5 jars of jam, so this all worked out fine!