I have found that 1and1 continue to have the cheapest domain names. And they have automatic renewal which is very good for someone buying domains in bulk. They have a very easy to use system.
As for hosting, you really can't beat Webfaction. They are affordable and flexible and super super easy to use (especially if you are hosting multiple sites).
I've used a bunch of different hosts and registars and those two are hard to beat.
Godaddy and Hostgator are super popular, but I beleive that is because they offer amazing affiliate deals - not because they have a good product. I've used both on clients sites and they are frustratingly slow and difficult to use compared to my 1and1 and webfaction setup.