The following Java applet allows you to easily upload many files to a confluence page. Download the following this jar file. On most operating systems you can execute it simply by double-clicking. You can also run it from the command line using:
...
Once you run this file a dialog like this should appear:
Click "Add files" and select the files you want to attach. Then click next:
For more information see:
http://confluence.atlassian.com/display/CONFEXT/Confluence+File+Uploader