This post by Ray Sims is a great list of ideas on ways to increase/adapt informal learning … a few of my favorites:
For every new piece of formal learning, explore complementary informal learning opportunities — explicitly driving this exploration through process
Make contribution expected
Make feedback expected
Improve content findability. Obsessive attention to enterprise federated search, cross-linking, social tagging, content reuse strategies, etc
Improve people findability. Both expertise location applications and other means
The entire list of 25 is well worth pondering.