Once you finish Infinite Crisis, you should check out some of the One Year Later stuff. Basically after Infinite Crisis all of DC's titles jumped forward one year. Green Arrow's storyline was my favorite because it introduces a rivalry with Deathstroke that was adapted in the TV show Arrow.
Also, you HAVE to read 52. One of the best series DC has ever put out, IMO, and focuses on lesser known/less popular characters and details what happened in the one year after Infinite Crisis.
Avoid the follow up, Countdown to Final Crisis, like the plague.