No. The best answer here is from Scott, who ran down the primary ways you can finance conventionally.
There are also ways to creatively finance--often with owner financing. Generally, agents are less comfortable with these and, really, if you can afford to buy conventionally you probably should. However, other options requiring far less than 20% down (though it's all negotiable) are traditional owner financing, lease-options, lease-purchases, land contracts, contract for deed, wrap mortgages, and land trusts. There are drawbacks and risks to some of these that you may not encounter in a traditional purchase, but they may be worth considering.
Hope that helps.