I haven't read any of the Blackest Night ones yet as i am waiting for the #1-14 to come through so i can read it all the way to #60. Then i will have to have a look at the dedicated Blackest Night series.
I was thinking of starting to read Captain America, but seeing as it is #600 + in i though against it.
That's cool, as long as you start reading Blackest Night from GL #43. You can acquire all the tie in's through various other means. I wouldn't recommend buying them all because, well, that'll cost a bloody fortune! Brightest Day follows Blackest Night #14 and GL #53.
And it's good to keep up to speed on The Flash because as soon as Brightest Day ends, Geoff Johns' next crossover is Flashpoint and will continue on from Brightest Day, making The Flash the focal point of DCU.
Seriously, Batman R.I.P. is worth following. You only need to start reading it from The Black Glove storyline and follow it up to present day.
EDIT: As an aside, Marvel haven't done anything worth reading since Civil War, in my opinion. Their best writers have creator owned series outside of Marvel and it appears that by showing these creator owned titles all their love, their work on crossovers/events has become very poor. Which is a shame, really.
Mark Millar and Brian Michael Bendis are two good writers, but each of them have at least one other title outside of Marvel (Kick-Ass and Powers respectively being the best) which has lead to some very poor events over the past few years. Hell, Civil War was a rubbish crossover. By relying on rubbish writers like Greg Pak and Jeph Leob Marvel have been putting out some pretty poor content for a good four years or so now.