If you request the base URI, you will receive a list of options you can pick from. (The browse categories) You can achieve the same result by requesting /browse.ashx without any GET parameters.
Copy <opml version="1">
<head>
<title>Browse</title>
<status>200</status>
</head>
<body>
<outline type="link" text="Local Radio" URL="http://opml.radiotime.com/Browse.ashx?c=local" key="local"/>
<outline type="link" text="Music" URL="http://opml.radiotime.com/Browse.ashx?c=music" key="music"/>
<outline type="link" text="Talk" URL="http://opml.radiotime.com/Browse.ashx?c=talk" key="talk"/>
<outline type="link" text="Sports" URL="http://opml.radiotime.com/Browse.ashx?c=sports" key="sports"/>
<outline type="link" text="By Location" URL="http://opml.radiotime.com/Browse.ashx?id=r0" key="location"/>
<outline type="link" text="By Language" URL="http://opml.radiotime.com/Browse.ashx?c=lang" key="language"/>
<outline type="link" text="Podcasts" URL="http://opml.radiotime.com/Browse.ashx?c=podcast" key="podcast"/>
</body>
</opml> Browse inside of a category. You can also view all categories by requesting the browse endpoint without any GET parameters.
Copy <opml version="1">
<head>
<title>Local Radio</title>
<status>200</status>
</head>
<body>
<outline text="Stations" key="stations">
<outline type="audio" text="OctoStation" URL="http://opml.radiotime.com/Tune.ashx?id=s100000" bitrate="128" reliability="99" guide_id="s100000" subtext="TuneOut - Music" genre_id="g61" formats="mp3" show_id="p1225767" item="station" image="http://cdn-profiles.tunein.com/s12345/images/logoq.jpg?t=155664" current_track="TuneOut - Music" now_playing_id="s100000" preset_id="s100000"/>
</outline>
</body>
</opml> 