See also 101 Resources for Freelancers (mainly free web applications).
But the actual knowledge and the new distinctions you gain from reading are not the main benefit. My experience has shown me that the real benefit comes not from what you read but rather from the habit of reading. When you read a new book every week, you condition your mind to keep taking in new knowledge. Your thinking remains fresh and sharp. Your brain is always churning on new ideas, looking for new distinctions it can make. Every day you pour in more ideas, which your brain must find a way to integrate into your existing knowledge base. Frequent reading fires up your neural activity, even during the periods when you aren’t reading.
Of course, reading web pages is a kind of reading, but not as intensive as book reading. I just love reading a book before going to bed. Even if it’s for 30 minutes or so, that reading is immensely pleasurable. Last night I read a letter from Paris to Helen in Ovid’s Heroides. Paris is trying to convince Helen to leave Meneleus for Troy. Tomorrow I’ll be reading Helen’s letter in reply. I can’t wait. (Btw, here’s a free online translation of Ovid’s Heroides by Tony Kline). Here’s more about Tony Kline.