These software tools are designed to aid AdSense publishers in getting a better understanding on how traffic flows through their site. Some will help you in understanding which keywords gain you more money and which locations give you the best AdSense payment.
One of the best such tools available is AdSense Gold (http://www.profitbooks.com/go/astracker) which allows you to have a better understanding of which ads and formats actually get more clicks and which are useful or nearly useless.
This program works by tracking views and clicks on all the publisher's pages. It even goes as far as offering you the possibility to see which referrer each visitor came in through.
There's a free tool called SynSense (http://www.singerscreations.com/RSS/Posts/235.asp) which is more of an AdSense monitoring tool. This sits in the tray and offers actualized AdSense stats as you hover your mouse over its icon. It's a very nice tool for those which like to be informed on how their AdSense is doing at all times of the day.
Google provides you with stats in a csv format on their site. So someone made a tool that can automatically download such files and extract a lot of information from them. The name of this tool is CSV AdStats and it is available from http://www.nix.fr/en/csvadstats.aspx?q=download
It has a large number of features, including the possibility to highly customize reported stats, exporting data and charts to other formats. It's in French but the language can very easily be changed to English.
Of course any tool can only access these stats as often as 15 minutes but the authors are well aware of that fact and none of these tools will get you in trouble with Google because of that.
If, however, you're browsing content most of the time, and your tool of choice is the Firefox Internet browser, there's an extension for this program that allows you to view the stats in your status bar.
Again, this software is aware of Google's 15 minute rule and enforces its usage, 15 minutes being the minimum time between updates. The Google AdSense notifier for Firefox can be obtained from http://code.mincus.com/?p=3
There is also a program called Golden Keywords out there that helps you in getting the best keywords for your site. It's really efficient and very easy to use. It does come with a price tag though, it costs $49.95 and it can be obtained from http://www.regnow.com/softsell/nph-softsell.cgi?item=8616-2
So as you can see, software developers are making more and more programs meant to help you in your quest to maximize your AdSense profits. But before you go out looking for them remember that Google has a few features of its own as well.
It does offer some reports (albeit a bit more limited) and using the 'channels' feature is a good way of finding out which ads on your site are really bringing in most of the revenue.
Be on the look out as new tools appear daily and make sure to invest time in your site, as that is the real key in success with AdSense.