One thing I would add to unknown's answer is RSS feeds. All the electronic resources mentioned: blogs, arxiv, journals, mathoverflow---they all have RSS feeds. Instead of compulsively looking at blogs each day for rare updates, or browsing arxiv all the time, I just go to my feed reader (mine happpens to be Google Reader).

Also some pages of interest may not have feeds. For those you can use a change detection service like http://www.changedetection.com/ which can send emails to you when a webpage changes. I for example use this to monitor the Assoc. of Symbolic Logic's list of conferences. I also use it to monitor certain publication lists of colleagues on their websites.

This can be a lot of information overload, but if one develops the habit of quickly scanning through the items, ignoring anything not of interest, then it isn't bad.