I recently had to expose the file extensions that we allow search to index outside of SharePoint.  Unfortunately SharePoint does not expose this out of the box.  So i had to write a web service to be deployed in MOSS that would expose the file extension list.

Here's the code I used to accomplish this...

FileExtensionService.cs

-------------------------------

using System.Collections.Generic;
using System.Text;
using msa=Microsoft.Office.Server.Search.Administration;
using ma = Microsoft.SharePoint.Administration;
using System.Web.Services;
using System.Web;
namespace Samples.SharePoint.WebServices
{
    [WebService]
    public class FileExtensionService
    {
        const string GetFileExtensionsCacheString = "FileExtensionService.GetFileExtensions";
        public FileExtensionService()
        {
        }
        [WebMethod(Description="Gets the Extensionlist out of moss")]
        public string[] GetFileExtensions()
        {

            List<string> extensions = HttpContext.Current.Cache[GetFileExtensionsCacheString] as List<string>;
            if (extensions == null)
            {
                extensions = new List<string>();
                Microsoft.Office.Server.ServerContext server = Microsoft.Office.Server.ServerContext.Default;
                msa.SearchContext context = msa.SearchContext.GetContext(server);
                msa.Content ssp = new msa.Content(context);
                foreach (msa.Extension extension in ssp.ExtensionList)
                {
                    extensions.Add(extension.FileExtension);
                }
                HttpContext.Current.Cache[GetFileExtensionsCacheString] = string.Concat(".",extensions);
            }
            return extensions.ToArray();
        }
    }
}