My favorite purging trick is to identify a "buddy" - someone who needs stuff, that you can pull things together for and take to them. Find a struggling mom to befriend at your church, in your child's class at school, on the Tribal areas for your state, another mom you meet at the playground who has younger kids. Then go through toys, books, clothes, gear, all that stuff with your "friend" in mind. Think how much she'd appreciate your things that are really JUST COLLECTING DUST.
Things that have sentimental value.... if it is covered in a layer of dust... if it is stored in a box under your bed.... if you have gone a year without really noticing it... then it really doesn't have the sentimental value you think it has. Get rid of a LOT of stuff. Then, the few things you have will be more prominently displayed and looked at more often. One baby outfit framed in a shadowbox on the wall, or one children's toy displayed up high on a sheld (not tons in a rubbermaid bin in the basement!). Fewer sentimetal things cared for a displayed better.
If you need the money (you want to buy a digital camera, let's say), then cut out a photo of what you want and tape it to a piece of paper. And then do a "yard sale" price list and go through a room totaling up how much you could make if you let this and that go for sale. Pretty quickly you will see how worthwhile it is to sell the rarely used treadmill, the outgrown clothes, etc. Dollars add up quickly when you purge a lot.
I agree with Heather, doing this with a friend makes a huge difference.