The four I'm currently looking at are namecheap, name, 1&1, pairnic and ghandi. The major appeal of 1&1, pairnic, and ghandi is that even though their prices are a bit more, they include privacy, instead of you having to pay extra for it.
I do see that you just end up paying for a year's extension when transferring, and can transfer them in bulk- so that part of the equation is solved. I've just only used network solutions and godaddy, so didn't know what was a good service. Two of them are also nameservers, but other than that, I don't have any special requirements.