ASP.NET offers a few solutions for handling long-running processes. One of the best methods is to combine threading with either a polling solution or AJAX.
If you struggle sometimes with XML's complex tree structure and syntax, you'll want to get your hands on (and your head around) XPath. XPath makes it as easy to view and query XML data as it is to work with a basic file structure. Find out what this simple tool can do for you.
A scripting engine, built in the language of your choice, and embedded into your application can make a huge difference to your customers, who have concerns about extensibility. Even better, creating a scripting engine is easy and fun. See three versions of a spam filter engine built in Groovy, Jython, and BeanShell.
As we race towards better object technology, some people seem content to put relational database systems out to pasturefor no good reason.