It's also possible to feed your house by "back-feeding" through your dryer, stove, or welder receptacle, but I wouldn't recommend it. There are two serious pitfalls to this approach, one is that you have to ensure the main power breaker is OFF before you connect the generator. It doesn't sound hard to remember, but it happens. A set-up like techman posted eliminates that possibility.
The second pitfall, and one that is potentially lethal, is that unless you completely disconnect the power feed from the utility to the main panel, it's possible under the right conditions to feed power back through the ground wire to the grid. Step that up through a transformer on the pole outside your house, and it gets really nasty. A repairman on a pole two blocks away can get a fatal shock from your generator.
With most main breakers on distribution panels, opening the breaker only opens the two "hot" leads, and does nothing with the ground wire. What the specific conditions are for this to happen, I can't say for sure, but I've been told that by people that work around this stuff for a living. I believe them.
The commercially available generator sub-panels and the Generlink break all three wires entering your house, two of those being live 110v to provide 220v service, the third being the ground wire to prevent that possibility.
Sean