USDA Rural Development financing doesn't have a minimum score requirement, and there are two versions, Direct & Guaranteed. Direct is where you go direct to USDA, and they do not have a score requirement like I mentioned, but it's a longer process (which you may not care about). The Guaranteed version is where you go through a lender, and most will have 620 or 640 score requirements. You have to buy in specific areas (Lancaster town isn't eligible, but east of Cemetery Rd/Bowen Rd is, south of William St is, and north of Walden Ave is), and your income must be within certain limits (the limit is lower for the Direct version). You can find the income limits & eligible areas at http://eligibility.sc.egov.usda.gov/eligibility/welcomeAction.do and USDA is 100% financing.
VA financing also doesn't have a minimum score requirement, but you need to be an eligible Veteran, and most lenders are looking for 600, 620 or 640 middle scores (your mileage may vary).
Conforming (Fannie Mae & Freddie Mac) loan programs are looking for at least a 620 score.
Those are the primary options today. There are non-conforming loan programs out there, but they only make about 2-3% of the total mortgages being made today, and are typically for borrowers with excellent credit but lack strengths in other areas (such as income, or buying an odd hard-to-market property, etc.), so probably wouldn't be something you should spend all of your time searching for (the effort & time would be better directed at improving your scores, even though you know I was going to say that).
All or most of which could be avoided if you just increase your FICO to 640 or higher.
Talk to a local and licensed loan officer experienced in credit rehab and FHA financing to assist you further. Hope this helps.