Comprehensive SEO tools? Here we go:

[boron]

You input one URL or keyword and you get many information - this is comprehensive ("All in one" ).

WEBUILDPAGES: (http://www.webuildpages.com/cool-seo-tool/) MSN/Yahoo, domain date!,backlinks, pages indexed, Alexa, .edu links, allinanchor.
URL-TRENDS (http://www.urltrends.com) (PR, Alexa, BACKLINKS: Y/G/MSN, DMOZ, title tag.)
URL-INFO (http://www.faganfinder.com/urlinfo/): TRANSLATOR (realy many European languages, bad performance anyway, lol) CACHE, PAGE CHANGES, TEXT ANALYZER...
Link extractor (http://www.iwebtool.com/link_extractor)
Keyword competition/suggestion (http://tools.seobook.com/general/keyword/). Shows top 10 sites in G/Y/MSN for aa keyword...

iwebtool.com, linkwendor.com, seochat.com, seotools.biz, webconfs.com, sitening.com are all full of SEO tools, but you have to use them one by one, so don't post them more. Only "one click - more results" tools, please :) . I checked all above and picked out the best SEO tools (http://www.marketingchat.org/forum/seo-links-compilation-t1199.html).

[Reckless]

i really like URL-trends, everything you need on one page

[boron]

URL-trends is also incorporated in
Golexa search tool (http://www.golexa.com/), which shows 1,000 URLs for a keyword and then for EACH URL:
-Google PR, Alexa Ranking, G/Y/MSN position
-Google cache, Google text only, Google "related:" (shows related sites)
-Source code
-email URL to the friend, Monitor this URL
-Translate Page, Spell Check, definition in Answers
-Link popularity, Keywords
-WHOIS
-Traffic charts from Alexa
-WayBack: Shows ALL versions of the site from its beginning.
-Loading Speed/Site size ratio
-PING
-IP Geolocation
-which Adsense Adds will be added on the site
-Backlink Alert (you get alert when a site gets a backlink)
-Yahoo Site Explorer
-Extract content from the page
-bookmark in del.icio.us and Yahoo MYWEB marks

You have to click on each tool, but you basicaly enter a keyword (URL) only once.