Every webmaster (at least that I know of) wants to know how the search engines see and evaluate their websites ... especially how Google sees them. Google webmaster tools was created with this concern in mind.
Anyone who has used them knows how important tools those are; You can see information Google collects about your websites, see what matters for their index and it includes also tools that you can use to help Google "see" (crawl) your sites easier.
The tools were recently updated (1 1/2 month ago I realized the changes) and they contain even more useful stuff for anyone that owns a site ... I am going to give a brief description of the most important things one can find when visiting the tools ...