As I constantly talk about in my how-to-get-more-women-into-technology talks, we, the developers, the people who do this job, need to get out there and tell people what's so great about what we do.
Some of the initiatives you can get involved in are collected here. Please mail me or get me on twitter (@trisha_gee) if you want to add anything to this list:
Devoxx For Kids (contact me or Dan Hardiker if you're interested in the UK)
Young Rewired State
Code Club - after school coding clubs for kids 9-11
Apps for Good - young people (11-18) learning to create applications to change their world
EPiK (Encouraging Programming in Kent) - mentor young people (8-25)
Meet a Mentor - mentor undergraduates/graduates in London(ish). Always looking for mentors of any experience level
JUGs and other user groups - join a local JUG! There's no better way to meet people who can mentor you, and influence you own peers. Being part of the London Java Community literally changed my life.
Attend and/or speak at events and conferences