mh_and - 3:29 pm on Dec 23, 2011 (gmt 0)
Majestic and OSE. I use both. Majestic is updated more often while OSE has SEOMoz's quality indicators next to them so makes things easier.
Majestic has also fresh and historical data, while OSE doesn't. OSE is slower and has more downtimes, though being SEOmoz's pro member grants access to a lot of useful info inside.
Raven is pretty good for link managing and uses both Majestic and SEOMOZ data but has limits, so if you aren't too large you can use that.
I remember SEOMoz's Rand comparing his tools with Majestic somewhere in Quora, so you can try to find that.
Both majestic and OSE have free and paid options, but free is limited of course. There are free versions of SeoSpyglass as well.