Microsoft Outlook Configuration Analyzer is a free tool which will scan your Outlook profile (2007 or 2010) and report on any issues which might be causing you problems.
To use the program, first make sure Outlook is running, then launch the Configuration Analyzer and start a scan. On our test PC the progress bar estimated a very long scan time (ten minutes or so), but in reality it was all over in a few seconds, so very soon we were browsing the report to see what it had to say.
The first details you'll see are information on your Outlook configuration: your various profiles, all the addins and third-party modules you've installed, the Outlook updates installed on this system, and any settings issues the program thinks might be relevant.
Expanding various sections of the tree will tell you more about that particular topic. We clicked "Application Event Log Entries for Add-ins Load Time", for instance, and got a report on every add-in and how many milliseconds it took to load, very handy information if launch speed is a problem.
The more interesting details are usually to be found on the All Issues tab, though, where the Configuration Analyzer will highlight any problems it considers to be significant. These aren't always a big deal - on our test system it turned out we were missing a couple of updates, and had "orphaned files in the Outlook Secure Temp folder", but either way if you click the issue then you'll find a link to a Microsoft support page which tells you more about the problem and how to resolve it.
And if you want more troubleshooting help then you can always switch to the Tree Reports view, which displays more technical details on your Outlook setup (including any recent crashes).
The Outlook Configuration Analyzer isn't doing anything that surprising, then, but it does do it fairly well, and there is some genuine depth here (the program understands how to retrieve Active Directory Domain Services credentials, for instance, when necessary).
What's more, this version does extend the Configuration Analyzer in several useful ways.
It includes 75 new rules to help detect even more issues.
The program now automatically downloads new rules as they're created by the authors, so should improve automatically.
And the installation adds two new command line tools: CalCheck analyzes Outlook Calendars for problems, while OCATcmd.exe can generate custom Outlook scans from a script.