diff --git a/src/java/com/threerings/media/tools/ResourceIndexerTask.java b/src/java/com/threerings/media/tools/ResourceIndexerTask.java
new file mode 100644
index 00000000..68e57a90
--- /dev/null
+++ b/src/java/com/threerings/media/tools/ResourceIndexerTask.java
@@ -0,0 +1,61 @@
+package com.threerings.media.tools;
+
+import java.io.FileOutputStream;
+import java.io.FileWriter;
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.util.ArrayList;
+
+import org.apache.tools.ant.BuildException;
+import org.apache.tools.ant.DirectoryScanner;
+import org.apache.tools.ant.Task;
+import org.apache.tools.ant.types.FileSet;
+
+/**
+ * Creates a file that lists all the resources in a fileset out to an index file.
+ */
+public class ResourceIndexerTask extends Task
+{
+    /**
+     * Adds a nested <fileset> element.
+     */
+    public void addFileset (FileSet set)
+    {
+        _filesets.add(set);
+    }
+    
+    public void setIndexFile (String file)
+    {
+        _indexFile = file;
+    }
+    
+    @Override // documentation inherited
+    public void execute () throws BuildException
+    {
+        PrintWriter fout = null;
+        try {
+            fout = new PrintWriter(new FileWriter(_indexFile));
+            
+            for (FileSet fs : _filesets) {
+                DirectoryScanner ds = fs.getDirectoryScanner(getProject());
+                String[] srcFiles = ds.getIncludedFiles();
+                for (String filename : srcFiles) {
+                    fout.println(filename);
+                }
+            }
+            
+        } catch (IOException ioe) {
+            throw new BuildException(ioe);
+        } finally {
+            if (fout != null) {
+                fout.close();
+            }
+        }
+    }
+
+    /** A list of filesets that contain files to include in the index. */
+    protected ArrayList<FileSet> _filesets = new ArrayList<FileSet>();
+    
+    /** The name of the file to which we should write the index. */
+    protected String _indexFile;
+}
diff --git a/src/java/com/threerings/resource/NetworkResourceBundle.java b/src/java/com/threerings/resource/NetworkResourceBundle.java
index 1f184d7a..8bb79f6c 100644
--- a/src/java/com/threerings/resource/NetworkResourceBundle.java
+++ b/src/java/com/threerings/resource/NetworkResourceBundle.java
@@ -28,6 +28,7 @@ import java.net.HttpURLConnection;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.security.AccessControlException;
+import java.util.HashSet;
 
 /**
  * Resource bundle that retrieves its contents via HTTP over the network from a root URL.
@@ -35,6 +36,11 @@ import java.security.AccessControlException;
 public class NetworkResourceBundle extends ResourceBundle
 {
     public NetworkResourceBundle (String root, String path)
+    {
+        this(root, path, null);
+    }
+    
+    public NetworkResourceBundle (String root, String path, HashSet<String> rsrcList)
     {
         if (!root.endsWith("/")) {
             root += "/";
@@ -45,6 +51,8 @@ public class NetworkResourceBundle extends ResourceBundle
             Log.warning("Created malformed URL for resource. [root=" + root + ", path=" + path);
         }
         _ident = path;
+        
+        _rsrcList = rsrcList;
     }
 
     @Override // documentation inherited
@@ -57,6 +65,11 @@ public class NetworkResourceBundle extends ResourceBundle
     public InputStream getResource (String path)
         throws IOException
     {
+        // If we can reject it before opening a connection, then save the network latency.
+        if (!inResourceList(path)) {
+            return null;
+        }
+        
         URL resourceUrl = new URL(_bundleURL, path);
         HttpURLConnection ucon = null;
         try {
@@ -91,6 +104,15 @@ public class NetworkResourceBundle extends ResourceBundle
         return ResourceManager.loadImage(in);
     }
 
+    /**
+     * Returns whether we believe the path to be available.  If we have no list, we assume
+     *  everything may be available.
+     */
+    protected boolean inResourceList (String path)
+    {
+        return _rsrcList == null || _rsrcList.contains(path);
+    }
+    
     /**
      * Returns a string representation of this resource bundle.
      */
@@ -105,4 +127,7 @@ public class NetworkResourceBundle extends ResourceBundle
 
     /** Our root url to the resources in this bundle. */
     protected URL _bundleURL;
+    
+    /** A list of all the resources included in this bundle. */
+    protected HashSet<String> _rsrcList;
 }
diff --git a/src/java/com/threerings/resource/ResourceManager.java b/src/java/com/threerings/resource/ResourceManager.java
index 075c03f8..a85d0c8c 100644
--- a/src/java/com/threerings/resource/ResourceManager.java
+++ b/src/java/com/threerings/resource/ResourceManager.java
@@ -36,6 +36,7 @@ import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Enumeration;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Properties;
@@ -655,6 +656,16 @@ public class ResourceManager
         return config;
     }
 
+    /**
+     * If we have a full list of the resources available, we return it.  A return value of null
+     *  means that we do not know what's available and we'll have to try all possibilities.  This
+     *  is fine for most applications.
+     */
+    protected HashSet<String> getResourceList ()
+    {
+        return null;
+    }
+    
     protected void initResourceDir (String resourceDir)
     {
         // if none was specified, check the resource_dir system property
@@ -698,7 +709,7 @@ public class ResourceManager
                 dlist.add(bundle);
             } else if (setType.equals(NETWORK_SET_TYPE)) {
                 NetworkResourceBundle bundle =
-                    new NetworkResourceBundle(_networkRootPath, path);
+                    new NetworkResourceBundle(_networkRootPath, path, getResourceList());
                 set.add(bundle);
             }
         }