I have also seen suggested that instead of having a single Someday/Maybe list, you split that into two lists.
1) A Someday list for things you know you will be doing in the future but you're not working on right now.
2) A Maybe list for things you're not sure that you will ever do.
I've been doing this for a few months now and I like it a lot. It helps keep the lists to a more manageable size.