It can be accessed here:

http://www.codeproject.com/useritems/MossAjaxWebPart.asp

It can be accessed here:

http://www.sharepoint-tips.com/2007/05/sharepoint-designer-article-2-creating.html

Valid:
<And>
 <Eq><FieldRef Name=”Title”><Value Type=”Text”>Value</Value></Eq>
 <Eq><FieldRef Name=”ContentType”><Value Type=”Text”>Product</Value></Eq>
</And>

<Or>
 <Eq><FieldRef Name=”Title”><Value Type=”Text”>Value</Value></Eq>
 <Eq><FieldRef Name=”ContentType”><Value Type=”Text”>Product</Value></Eq>
</Or>

Invalid:
<And>
 <Eq><FieldRef Name=”Title”><Value Type=”Text”>Value</Value></Eq>
 <Eq><FieldRef Name=”ContentType”><Value Type=”Text”>Product</Value></Eq>
 <Eq><FieldRef Name=”Field1″><Value Type=”Text”>Value</Value></Eq>
</And>

<Or>
 <Eq><FieldRef Name=”Title”><Value Type=”Text”>Value</Value></Eq>
 <Eq><FieldRef Name=”ContentType”><Value Type=”Text”>Product</Value></Eq>
 <Eq><FieldRef Name=”Field1″><Value Type=”Text”>Value</Value></Eq>
</Or>

You can wrap AND/OR nodes in other AND/OR's.  If you need three conditions, you would do the following:

Valid:

<And>
 <And>
  <Eq><FieldRef Name=”Title”><Value Type=”Text”>Value</Value></Eq>
  <Eq><FieldRef Name=”ContentType”><Value Type=”Text”>Product</Value></Eq>
 </And>
 <Eq><FieldRef Name=”Field1″><Value Type=”Text”>Value</Value></Eq>
</And>

<Or>
 <Or>
  <Eq><FieldRef Name=”Title”><Value Type=”Text”>Value</Value></Eq>
  <Eq><FieldRef Name=”ContentType”><Value Type=”Text”>Product</Value></Eq>
 </Or>
 <Eq><FieldRef Name=”Field1″><Value Type=”Text”>Value</Value></Eq>
</Or>

If you need more conditions, you need to get creative with your wrapping, but it can be done.

     Guid g = {GUID};
     SPSecurity.RunWithElevatedPrivileges(delegate()
     {
         using (SPSite site = new SPSite(SPContext.Current.Site.Url))
         {
             SPSiteDataQuery query = new SPSiteDataQuery();
             query.Webs = "<Webs Scope='SiteCollection' />";
             query.Query = string.Format("<Where><Eq><FieldRef Name="UniqueId" />" +
		+ "<Value Type="Text">{0}</Value></Eq></Where>", Convert.ToString(g));
             query.RowLimit = 1;

             using (DataTable dt = site.RootWeb.GetSiteData(query))
             {
                 foreach (DataRow dr in dt.Rows)
                 {
                     Guid webId = new Guid(Convert.ToString(dr["WebID"]));
                     Guid listId = new Guid(Convert.ToString(dr["ListID"]));
                     using (SPWeb web = site.AllWebs[webId])
                     {
		          SPList list = web.Lists[listId];

		          SPListItem li = null;
		          try
		          {
		              li = list.Items[ g ];
		          }
		          catch { }
		          if (li != null)
		          {
		              // Now you have your item, do what you need to do
		          }
		          list = null;
                     }
                 }
             }
             site.RootWeb.Dispose();
         }
     });

These are the features listed on their site:

Enhance Internet Explorer's Tabbed Browsing Capabilities
1. Double click to close tab.
2. Open new tab from address bar.
3. Enable/disable tab browse history manager.
4. Enable/disable crash recovery
5. Move the IE menu bar above the address bar
6. Hide search bar.
7. Modify the maxium number of parallel connections to the web server.
8. Select the external program to view page source 

AD Blocker
Blocks all forms of advertising, including Flash ads, rich media, fly-ins, slide-ins, pop-ups, pop-unders, spyware and adware ads, and messenger ads.

Super Drag and Drop
With 'Super Drag and Drop' enabled, you can open new links by simply dragging and dropping the link on the page. You can also Drag and Drop to search selected words with the default search engine or save the selected photo when Shift is held down.

Mouse Gesture
Mouse Gesture allow the user to execute commonly performed tasks (open/close a tab, go back, go forward , print , scrolling page etc.) by drawing a simple symbol on the screen.

Crash Recovery
Crash Recovery automatically restores all opened pages after a crash happened.

Save Page to Image
Flexible and easy-to-use tool that converts html page from any URL to image. It captures the whole web page's content into JPG, BMP , GIF , PNG or TIFF on the fly.

Quick Proxy Switcher
Different internet connections do often require completely different proxy server settings and it's a real pain to change them manually.

Greasymonkey alike User Script
IE7Pro Script is to Internet Explorer7 as Greasemonkey is to Firefox. It lets you remix the Web via scripts.