Yes, some of the links in this article are affiliate links, I might be evil and biased and out to rip you off, FCC requires me to say this, etc. blah blah.
I've been rejiggering my SEO toolbox lately: I used to focus on the 'cool' stuff - things I thought would impress clients, generate pretty reports, etc.. I've really switched to emphasize big labor-savers, instead - tools that are versatile, let me work with raw data and the like.
Here's what I'm using these days:
When SEOMOZ launched their latest toolset, I nearly flung myself into the Green River. See, I've been slowly chipping away at an advanced toolset that would:Crawl web sites automatically;Diagnose potential onsite SEO problems;Generate easy, readable reports and alerts based on the diagnosis.
Then SEOMOZ came out with their Pro toolset, which:Crawls web sites automatically;Diagnoses potential onsite SEO problems;Generates easy, readable reports and alerts based on the diagnosis.
But, their tool rocks. It's super easy to use. Even cooler, it lets you download a crawl diagnostics file that you can filter through in Excel, generating your own reports. I'll be doing a video tutorial on that pretty soon.
And of course, when you sign up, you also get access to Linkscape, all their nifty content, and their Q&A service.
You can get a tour of the toolset here.
Aaron's SEOBook is best known (I think) for training content and the forums.
He's also got a kick-ass toolset. Some of the tools are free, so you can give 'em a test run. There's SEO for Firefox, of course, and the SEO Toolbar. Plus the keyword suggestion tool.
The really cool stuff, though, is under the pay account. With membership you get access to a suite of great domain research tools, a competitive research tool and my favorite, the SEO Site Planner, which makes generating a keyword map a breeze.
Like SEOMOZ, a subscription is pricey, but it only has to save me 4-5 hours a month to pay for itself, and it more than takes care of that.
You can check out SEOBook here.
I've already written about this lovely command-line tool here. You can read up. It's geekery, but it's the Swiss Army Knife of search tools.
Another great link research tool, Majestic has something SEOMOZ's Linkscape doesn't have (yet): It shows link growth over time.
That's pretty important when clients start asking 'what have you done for me lately?'
You can also compare backlink histories between sites, check for other sites on your server, and generate pretty reports.
Check out Majestic SEO here.
If you're serious about really getting into the weeds in SEO, you probably need to learn Python, or Ruby, or PERL (if you enjoy punishment).
All of these languages will let you create a crawler and include some nifty libraries for web crawling, parsing HTML pages and other geekery.
Can you be a good SEO without learning any of them? Absolutely. But if you want to really understand how a crawler 'thinks', nothing beats building one. I use Python scripts now to test sites, track link building campaigns and apply Latent Dirichlet Allocation (LDA).
I'm a nerd, so I enjoy this stuff. If you're not, ignore this one and move on.