In this recent post to his blog Brian Smithwick talks about the "locked box" that developers can sometimes restrict themselves to - getting to comfortable in the tech they already know and not branching out.
Jason Austin gave a great presentation at CodeWorks Raleigh recently about cultivating one's passion for software development through side projects -- safe spaces where we can play with new technologies and techniques. The point's well taken: as developers, we're probably putting most of our energy towards the thing that must be solved, that keeps us employed, that pays our bills. [...] And so all of us, at one time or another, end up in a backwater of our own devising -- a locked box.
He also puts an emphasis on collaboration and community as it relates to becoming a better developer. By interacting with other code and other projects' developers, you learn not only more about other ways to develop but are exposed to ideas you may not have come across on your own.
I'd add that active participation in the local community is just as important though: the opportunities for exposure to new ideas outside your sphere are greater than your feed reader will probably provide, and the depth of information that you can get in a conversation may be better than any blog post or man page.