It depends, are you looking for an analysis of your pagerank, backlinks, keywords, etc? There are quite a few SEO tools you can via when you Google "SEO tools". Many are free.
Would be helpful if you could be more specific in what you're hoping to find out about your site.
If you're looking just for general info about seo and page load time averages and rankings, then i'd suggest just good old google web tools (http://www.google.com/webmasters/)
You'll get info on page load time averages over a long period of time, with tracking by google spiders - Along with a comparison to average load times as google sees it. You'll also get info on general page errors and suggestions in html.
It's not the greatest, and can be useless in some manners, but it definitely still has its uses.
I was interested that rankingtoday/com put a limit of ten meta keywords where as scrubtheweb/com seen not too fussed so i was basically just wishing for a few more sites that look over the meta discription and meta tags