How does one keep herself updated with new research without forgetting older results?
Here are a few additions to Suresh's list (converted from a comment at TCSgrad's suggestion):


Don't even try to remember details. Just remember that somebody published something related, and use Google (or Mendeley or Papers) to find the paper again when you need it.
Chase references. Interesting papers tend to cite other interesting papers.  When you read any paper, also look at the papers in its bibliography.
Chase citations.  Interesting papers tend to be cited by other interesting papers.  When you read the paper, find other papers that cite it (via Google Scholar, for example) and look at them, too.
Follow whims.  If you see a paper with an interesting word in the title, or an interesting figure on the first page, at least read the abstract.
Don't try to read everything. That's impossible. Just try to read a little more.
Stop reading.  Eventually you have to do your own research.  Don't worry about reinventing the wheel; sometimes the best (and even fastest) way to understand what someone else did is to ignore them, figure it out yourself, and then read their paper.