I've used a credit union, bank, and mortgage broker. It all depends on the broker, the bank or the credit union you go to. A good one is worth his weight in Miatas. They'll work for you and guide you every step of the way. The trick is to find one with your interests at heart. They may be hard to find, but ask around and see what names come up. A mortgage broker can also "shop" you around to get you the best deal. These days it does take a fair amount down unless you go FHA, which has been mentioned already.
One quick note. Our renters have been trying to buy for a year now, with not much luck. The wife has a credit rating of 780, the husband 590. They cannot get a loan at all right now with his rating. It's tough right now, so save up and get your score up. Your score is VERY important. I even had them go to our broker, who is a friend, and she wan't able to help them either.