XML sitemaps, as defined by Sitemaps.org, are a standard way to inform search engines about the content of your web site. While in many cases your site will be automatically crawled for new content, there may exist pages without any direct link. Using an XML sitemap is a way to let the search engine know about its existence.
I have spent the last days on optimizing performance of the Imtech SharePoint Enhancement Toolkit: a toolkit that I have built in order to achieve standards compliancy, accessibility and slightly better performance of Web Content Management (WCM) solutions built in SharePoint 2007.
Content Query Web Part (CQWP) is probably the best solution for data aggregation within SharePoint 2007 solutions. The limited functionality exposed through the standard UI is compensated by caching and high performance of the CQWP. Yet there is one thing that can keep you off using the CQWP in environments which require you to deploy your solutions including the configuration in a fully structured and repeatable manner.
Lookup Fields as we know them
I create very often little projects to try things out: either based on the Console Application or the Class Library template. As it's SharePoint development we're speaking of the first thing you need to do is to add references to the Microsoft.SharePoint assembly. Depending on what you're doing you might need to add the references to System.Web and Microsoft.SharePoint.Publishing as well or maybe even more. You can do it just the regular way by clicking with right button on the project References and adding new reference but there is a faster way.