Usability 
Tickets.com, a major online ticket broker owned by MLB.com (Major League Baseball) has launched a mobile version of their service at mobile.tickets.com. Tickets.com handles tickets for events around the world ranging from chamber music concerts to professional wrestling.
The mobile site uses a two-level hierarchical menu with top level categories of "Sports", "Concerts", "Arts" and "Family Events" each of which is divided into a dozen or more additional categories. There's also a search box.
Mobile ticketing is something I'd be likely to use when, for example, I'm out with friends and someone gets the idea that it might be fun to go to a comedy club. Unfortunately this site has a serious usability flaw, especially for mobile. There is no way to filter events by location or date. In the mobile context, you generally want something today and nearby. Clicking one of the subcategories returns a list of all events of that genre anywhere in the world for the next two weeks. I don't see that as being very useful.
I tried to find a way to make it work for finding a comedy performance here in San Francisco, preferably tonight. I launched mobile.tickets.com and clicked on Arts (comedy IS an art) and found nothing, so I did a search for "comedy" and see that it's under concerts. I go there and get a huge scrolling list of about 60 comics and venues, just their names. I click a few and see that they are performing somewhere thousands of miles away or a week from now, not helpful. A search for "comedy San Francisco" returns hits for the main comedy section listing the 60 comics and for the the San Francisco Giants, 49ers and Symphony. A search for "comedy and San Francisco" returns nothing, again not helpful.