Well here is the XML for this simple OMC command; the DOCTYPE entry is one row with a space; shown here on two rows for a narrower display.
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>COMMAND_LIST</key>
<array>
<dict>
<key>ACTIVATION_MODE</key>
<string>act_selected_or_clipboard_text</string>
<key>COMMAND</key>
<array>
<string>open http://redirect.nyud.net:8090/?url=</string>
<string>__OBJ_TEXT__</string>
</array>
<key>ESCAPE_SPECIAL_CHARS</key>
<string>esc_with_percent</string>
<key>EXECUTION_MODE</key>
<string>exe_silent_popen</string>
<key>NAME</key>
<string>Coral Cached URL</string>
<key>NOTES</key>
<string>This will open a Coral Cache of the selected
URL, which saves sites from being Slashotted. Coral Cache is great as
it allows you to view the site if someone else already used Coral Cache
on the URL when it is unavailable. Submitted by Kenn Herman</string>
<key>SUBMENU_NAME</key>
<string>..</string>
<key>VERSION</key>
<integer>1</integer>
</dict>
</array>
<key>VERSION</key>
<integer>2</integer>
</dict>
</plist>
[robg adds: I got this working by using the OMCEdit application that's included with OnMyCommand. There may be a simpler way to do it using the above XML file, but I just created a new command in OMCEdit. This screenshot [78KB] shows the settings I used. It works as described...]

