I recently saw this question making the rounds and thought I should take a moment to answer.
First off let me post a link.
This is the site you want to go to for all the nuts and bolts of the USDA (Rural Development) Loan
The gist is you get 100% financing for a qualified house if you are a qualified buyer. Use the link above and follow the tab labeled ELIGIBILITY.
The property will need to be in a rural area as specified by USDA. They have a link on the site that allows you to look up an address to double-check. On a side note in March 2013 the boundaries will be changing so a house that qualified last month may not qualify next month.
Maximum Adjusted Household Income for Charles County, Maryland is $101,000.00 annually for a family of 4.
If you want to work through the process and get pre-approved speaking to a loan officer (I would be happy to supply a few names) is going to be your best bet.