If there's one thing I love almost as much as organizing, it is beautiful pie charts and graphs. ;)
Here's a great article, written after a pretty exhaustive survey on our spring cleaning habits. I really love I Heart Organizing, too. Make sure to follow Jen for gorgeous before and after photos and DIY tips.
My take on spring cleaning is simple: clean and organize when it's necessary. If springtime makes you want to open your windows (and your closet door) for fresh air, go for it. I try to keep on top of decluttering all year by immediately discarding anything that no longer works in my life. I keep a box or grocery bag that is for donations and discard items when I decide I don't like it, or I get a new one. That makes it easy to decide you don't need one item. Just put it in the bag. When the bag is full, I pack it into the car and drop it off when I do my other errands. This really helps keep my closet and my kids' closets under control.
If the drawer won't close, something has to come out of it. If you can't find your favorite coat because the coat closet is a mess, time to tackle it. If you're overwhelmed by you linen closet, time to purge. I try to focus on one small area at a time, just the linen closet for example. I'm not sure if most people realistically have the stamina to declutter their whole house, even over the course of two months. For me, the key is break the job down into manageable parts. Perhaps only one shelf of the bookcase today.
Go easy on yourself. Stay focused on one small area and do a great job. That's how you build momentum. Happy spring cleaning!