It is estimated that professionals learning informally for 80% or even 94%. Personally I'm convinced of this principle though semi-formal events or workshops can play a crucial role in directing learning. As Harry Vos states in his dutch blog "more formal or workshop learning supports informal learning and not the other way around". At the one hand, it is surprising how we focus on formal events, on the other hand it is tempting, also for myself, because they are so much more visible. Informal learning on the other hand seems invisible and a natural process that doesn't need a helping hand, after all people group around the coffee machine automatically. However, you can stimulate informal learning, bringing you as a facilitator in the grey area in between formal and informal learning.
So far I've focused on learning in communities of practice and networks, but there is more to it and I would like to explore the other forms more (including social media ofcourse!!). Together with Sibrenne I've facilitated a learning network for two years. After the two years nobody wanted to continue facilitating it. Interestingly, I have the feeling the informal netwerking and exchange is still going strong. Many of the people I'm still meeting and exchanging with, though not as structured and there are no meeting any longer. It is 'underground learning' and not as accessible to everyone. So facilitating a community of practice or learning network is a great example of the way you can stimulate individual learning to become collective learning- and at the same time, it catalyzes individual learning by the participants (in a dynamic network ofcourse).
But what else can you do to stimulate informal learning processes in organisations? The European PILIP project has created a website about informal learning. It has a quickscan to map informal learning processes which allows you to zoom in on factors that stimulate or hinder informal learning. You might work on those, to catalyze more rapid and effective informal learning processes. You can find a toolbox with tools like intervision, best practice storytelling, etc. I haven't used it yet, but I'm planning to go through it for an upcoming session with a development organisation.
A nice example: I experienced one that a worker was very active in formulating her learing questions, mobilizing relevant colleagues and inviting them for a lunch about the topic. A stimulating factor and positive example! What you can do is name this (literally, give it a name like peer-assist-lunch and stimulate others to copy this practice, for instance by creating a budget to cover for the lunch costs.