I just found out that the object model includes some very useful classes to speed up your coding efforts.

SPUtilty

Contains methods for redirecting users to the error page, access denied page or a custom url. You can get Full name and email adres of a user by passing in the logginname, send an email from the web context or determine if an lcid is an East-Asian lcid.

More information here: http://msdn.microsoft.com/en-us/library/microsoft.sharepoint.utilities.sputility.aspx

SPBuiltinFieldId

Contains variables for all the Guids of the built in fields. No need to worry about the difference between dutch and english MOSS sites.

SPBuiltInContentTypeId

Contains variables for all the Guids of the built-in contenttypes.

SPDiffUtilty

Shows the differences between two strings in Html format. So comparing “This is an initial string” with “This” returns the following: “This is an initial string“

SPContentTypeId (structure)

Provides methods to determine the relationships between two contenttypes.

SPContentTypeUsage

Allows you to determine where contenttypes are used within the sitecollection. Here’s a useful post that shows code to audit the contenttype hierarchy: http://soerennielsen.wordpress.com/2008/03/06/audit-your-content-type-hierarchy/

SPChangeQuery

Allows you to query your sitecollection for objects that have changed. This way you can audit changes in access rights for instance.