Majestic SEO - Awesome back-link database. I've had alot of fun digging through there.

SEOMoz - Linkscape is pretty good to find back-links on competitors. Their rankings tool is also pretty good. Can't say many bad things but the tools are decent enough.

SEOBook tools - I've only used their RankChecker (totally free) and their other plugin. RankChecker technically pulls 100 results at a time. This skews things because it will bring up indented results that normally wouldn't be on the first page (for example a 4th listing could look like a 6th in the tool since two listings above it have second listings in the top 100 but that weren't originally on the first page). I imagine the rest of the tools are decent considering that Aaron has been on-top of things for years now.

Raven SEO Tools - Popular right now. What i've seen is pretty basic but decent. More of work-flow types of tools and google analytics integration.

Covario looks like they have a decent tool set.

Things I use: Xenu's link sleuth, W3C Validator, Firefox plugns: Link Checker, User Agent Switcher, Web Developer, SearchStatus, SEO Quake, and Firebug.

Occassionally I've used Domain Tools.

Every SEO should atleast do a free Majestic verification, quantify with quantcast, set up google analytics (or a better tool if available), set up webmaster tools for all engines, set up google ad planner, make good use of google alerts,... Info info info!

@ sciongeneration... Hi there, that's a good list of other SEO tools to use, in conjunction with SEO PowerSuite top rankings are as good as asured!

All I would add to your list, and I feel it is actually the biggest, best, fastest, most accurate SEO Tool available... Google (the search engine)!!! ...ok well I mean in conjunction with 'search operators' like 'site:', 'inanchor:', 'intitle', '~' etc
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Expert SEO help & advice from the SEO Expert in Cheshire UK - SEO Chester.