http://www.myfico.com
Anyone who wants to get a good insight as to how certain things effect your credit score should sign up for credit watch at myfico. It's like $8 per month and it will alert you to changes on your report when they impact your score. That will allow you to see in real time how different things effect your score. HIGHLY RECOMMENDED.
Example- since I have this service, I watched my credit score tank from 740 down to 680 because I had a bunch of business debt on my personal credit cards. I am currently working on getting financed on a $540,000 piece of property. Since I knew my score was impacted so negatively by the high revolving debt, it gave me the opportunity to shuffle the credit card balances temporarily out of my name and it brought my score back up to around 750.
This equates to a savings of about $300 per month because with a higher credit score your mortgage rate goes down.
Also read "From Credit Repair to Credit Millionaire" by Donna Fox. GREAT info on building and repairing credit.