My hands down favorite is Fabulous.com right now. Caveat is they cater to large portfolios and certain extensions (com/net/org/info). They don't screw you over on anything though. Even if your names expire and someone buys it through drop process, you get a cut of the sale. They don't keep any domains for themselves. Prices (for portfolio holders, retail side is as expensive as Netsol/register.com) are barely above cost.
Since Fabulous isn't available for most of you (unless you want to pay retail). I would recommend NameCheap.
I have a personal goal of one day consolidating my domains with at Fabulous :) I'm getting there. In the short term I have my own private label registrar through Directi that isn't to shabby.
I think I'm paying around $8.50 USD per domain, with privacy included.
Bulk management is a bit of a pain - but that's what DomainManager is for :)