Developer Collaboration / Knowledge Sharing

As a consultant for a large company you are often segregated from your peers, often by physical location, for what can be extended periods of time.

For me this poses a very important problem, and that is the sharing of knowledge within the company. When a developer goes out to a client, they can build a vast range of knowledge that is never then shared back to the broader development team. Sometimes even knowledge within a team at a client site is not shared effectively, leading to a lack of growth within the team, and lack of understanding and standardisation within the delivered products.

Formal training can be used to bring everyone to a certain level of knowledge, but training rarely imparts the knowledge of best practice or the results of experience.
Developer-led workshops are often better at imparting specialised knowledge but they are dependent on attendence, prerequisite knowledge and can suffer from a lack of follow-up material. It can also require significant time investment on the team, where physical segregation and time management has significant issues.
Wiki's and blogs can provide as much information as developer-led workshops, but suffer from lack of accessibility and relevance, and the lack of immediacy of queries and responses, so while it is a useful way to store information, it is not always useful for sharing information.

For me, the above scenarios seem to be the most commonly used way to share information, and do help to at least some degree. However it is also lacking in so many ways to really bridge the gap of knowledge within a large group of developers.

I think the popularity of social media shows how easy it can be to share information between peers if it is easy to share, and easy to search. Stack Overflow is an outstanding example, where the community is answering the questions of other developers and in the process sharing their own knowledge and experience. I would like to see something that is almost the opposite of this as well, where developers can share snippets of code that they have used to solve a particular issue, or that can be extremely useful in a variety of situations. CodeProject is a bit like this, but the 'gamification' and 'accessiblity' of stack overflow makes it a significantly more relevant tool.

So for those of you working in the industry, how do you ensure everyone has access to the knowledge and experience of your most effective developers.