SEO experts love to measure. They loved measuring PageRank, rankings and traffic and they still need something to follow this urge. Well, there still is a lot to measure beyond strict business or usability metrics. Old school SEO still makes sense in lots of cases, especially with backlinks which still determine above all your success in Google search. I’d concentrate here on Google, but on the US market it still also make sense to check these with Yahoo and others. Also, checking backlinks with Google is not fun (only a fraction of data is released by Google unless you check your own site in Google Webmaster Tools) so you’re advised to measure them with Yahoo tools are tools that measure it using Yahoo data.
number of backlinks
You still need to know how many people or rather pages link to you. especially if this week more or less do it. The sheer number may be meaningless if you have 10.000 links from one site though. So focus also on domain popularity (links from one domain counted as one).
quality of backlinks
Getting a ton of links may mean nothing in comparison to one link from the NYT. So determine the quality of links: Has the linking page many other outgoing links? Has it PageRank? It it an old authority domain etc.?
Google cache date
Many SEO specialists resort to checking the cache date in Google (Google saves most pages in a “cache”) for determining the quality and success of a website in Google. If the cache date is older than one month the site is either dead (no fresh content) or has a very low authority with Google. Of course you always should check whether a site has a cache at all. Not cached sites probably get de-indexed (penalized) by Google.
Google bot visit frequency
Your cache might be one week old, but if Google bot visits daily it’s OK in most cases. You can check with most server side web analytics solutions, those relying on server logs or PHP.
Last time Google bot visited
This is almost the same as above but only almost. If you have a new content page and the bot visited yesterday and you’re still not in the Google index something might be wrong (like duplicate content problems)
It’s seldom as simple as “the more pages indexed the better” but for small sites it often is. If you have 50 pages online but only 20 indexed your site is not successfully spidered by Google. A site:yoursite.com search in Google is enough to find out.
PageRank “pass rate”
While I argue that looking at the actual toolbar PageRank does not make much sense nowadays anymore you certainly want to take a look at the pass rate of PageRank. Google PageRank is passed via the links on your site. A home page with PR 5 should have subpages with PR 4 or at least 3, otherwise you have too many links or your internal link structure is broken.
While Alexa is not really reliable or never was many advertisers use it to check your traffic numbers. Also the Alexa traffic estimates can be compared to other sites, other time periods (more or les trafic this year than last?) and to other traffic estimation tools.
While Compete is said to be more reliable than Alexa it only is for US traffic. This is both good and bad news but at the same time allows, e.g. compared with Alexa, to see where you’re heading. If you server the US market, take a close look at Compete.