My solution to this is to have an entire file-system for someday-maybes (my "idea cauldron") and a "Pending" list for projects I will likely want to start/resume sometime in the next month (so that they don't get lost in the someday-maybe box), in addition to my Project list.
During my weekly review, I try to be ruthlessly honest about which of the projects I actually want to/ expect to make progress on in the next week or two, and shift any others to pending (or sometimes straight beack to someday-maybe). I review the "pending" list weekely, and the "idea cauldron" monthly.
The result is an active project list short enough that I don't need to categorize it. The "pending" list and the (neccisarily somewhat messy) organization scheme of my "someday maybe" cauldron are what save me, because they allow me to keep my active projects list short enough to be manageable.
Now only "truely active in the next week or so" projects go on my "project" list. The "I need to begin this soon" and "I need to get back to this before too long" and "I'd better not forget about this" do not, anymore.