The .NET Framework 2.0 contains a component called ReportViewer which can be used to generate reports in different formats (HTML, PDF, etc...).
After having used it for a couple of reports in a web application, I came to believe that the only good thing about it is that it's free (when used in Local mode).
Why? Because of its bug ridden designer!
First of all, it contains a nice "Data Sources" panel that should list all the functions (from your code) that can be used to feed the report. Wonderful. Too bad that unless you keep the Default.aspx page open it doesn't display anything.
Also, you should place the .rdlc file in your App_Code folder to get the "Data Sources" list to work. Too bad that when you publish your web site, the content of that directory will be ignored.
There are other bugs here and there, but come on... how can these two have not been noticed by Microsoft?