Suggestion the first: create a central hosting solution for anything developers think is relevant to learning. At a minimum, videos of presentations & brownbags should go here; screencasts, workflow videos and so on are also nice to have. If someone wants to write up a text document outlining how a design decision was made, or how they think an optimal code review process goes, let them! Ensure all contributions are voluntary. Date all materials clearly so that developers can judge for themselves how out of date they may (or may not) be. This can be as simple as a directory page on the internal wiki (you DO have an internal wiki, don't you?) or as complicated as a StackOverflow-type solution that allows for voting and comments.
The thing that kills me - especially about the large corporation I used to work at, but even about the startup I work at now - is how much knowledge is generated and then lost within the organization. This strategy helps mitigate that somewhat.
Suggestion the second: create an internal calendar of technical events relevant to the company's mission. Seed it with as much stuff as you can find (everything from CocoaHeads / user group meetings to panels on mobile development to...), then allow developers to add events themselves as they stumble across them. Bonus points if the solution allows them to RSVP and see who else from the company is going (Google Calendar does this); it helps build a sense of community and helps the devs know who shares and can discuss their interests.
Among what's already been said - +9000 on sending developers to conferences. Also have a well-publicized process for developers to identify training and say, "Hey, you should send me to this!", as well as clear expectations for what a developer will do when this training is approved (do they need to share out their notes to the rest of the company? give a brownbag on what they learned? etc.). Good developers usually know what they need to learn. Great developers usually know the most efficient way to learn it.