Welcome back.
There are so many projects that you have lots of choices. Generally I would say crunch whatever project makes the most personal sense or has the best interest for you.
The HOT project right now seems to be Folding@Home. I personally crunch on D2OL. Some folks are big on dFold, and there are those who are loyal to SETI and RC-5. The only one I would say don't waste your time with right now is Ubero.
My personal opinion is that Folding@Home and D2OL provide the best chance for good science that will benefit humanity. But just jump in anywhere and find what you like. Every project will appreciate the help.