MOSS 2007 has this cool little web part: Site Aggregator. Most have seen it on My Sites out of the box. It displays relevant documents and tasks for you, the user, across the sites where you are a member.  There are several web parts that are used only on My Sites; however, Site Aggregator is one of the few that can also be used in other sites.

The Site Aggregator is the simplest answer to the constant question: “How can I display content from different site collections in another?” It allows you to pull in this content with no code, and the security that is applied to the item is not affected.   

1.       Add the Site Aggregator to your page.

2.       When first added, the New Site Tab is displayed, enter the URL of a site into the Site URL field. In some cases, the Site Name will automatically populate, but you can enter your own value or change the default, then click Create.

3.       Click Sites, New Site Tab and enter a new URL and site name, click Create. Repeat to add all of the sites required.

You will notice that only the relevant documents or tasks for that user are displayed, you may want to change this behavior.  

1.        Click the drop-down on the right of the web part and select Modify Shared Web Part.

2.       Scroll down and expand the URL section of the properties.

3.       Delete “_layouts/MyInfo.aspx” from the URL to append to the site.  

4. Click OK.

Want to take it a little further? Don't show the full page with header, navigation, etc… from the site. Create a minimal master page, content type, and page layout to show only web parts. Create a page using this content type and add the content to this page, point your Site Aggregator to the URL of this page in each site you want to display. Your users will be able to view content that is contained in multiple sites from a single page, all without leaving their current site, and it will have the same appearance as the rest of the web parts on the page.

*TIPS*

If you want to display only specific information from a list or library for the page where the Site Aggregator is, add a Query String filter web part to the page you will be linking to and include the string in the URL to append to site when you enter it in the Site Aggregator. It will not affect the other pages, however, you can only do one Query String, so make it consistent across other pages if you need to filter more than one site.

Make sure you plan ahead when adding sites to the Site Aggregator. Once they are added, you cannot change the order, you can only delete them.

Since the Site Aggregator passes your login information (domain and username only) to sites, you may not want to include external sites as this could pose a security risk.