I'm the primary Marketo user in our company, but I try to involve others by teaching them what they can accomplish using Marketo. Most of the time this is basic stuff like pulling reports, since the technical projects come my way. For some people, they see the value in MA and knowing how to use it, but other people are more interested in other things, so it doesn't really take off for them.
Oh, and occasionally I try to get them excited by talking about how great the community is! 🙂