Ten in 2011
I found an interesting suggestion on another forum. A poster mentions that each year, she has ten New Year's Resolutions. These could be projects she wants to get done, good habits she wants to start, etc.
It's ten over twelve months on the assumption that there will be at least one month where nothing gets done and to take December off. The aim is to keep it manageable and have many small triumphs throughout the year. (On that note, you could just as easily do "Six in 2011", give yourself two months for each project/habit, make it even more manageable.)
I'm going to try it. Dunno what the rest of my projects will be, but at least two will be clearing my electronic clutter (emails, URL's, hard drive disorganization) in January and clearing our incoming mail in February.