Our gym has four Expresso Internet connected bikes. The bikes have virtual tours of various difficulty (and you can ride against a virtual pace rider), but when I'm unmotivated I have the most success with the Proving Ground mode. It's like a video game on wheels. You ride around collecting coins and chasing dragons of the corresponding color. If you catch the dragon you get points.
Months ago I created an Expresso account. If I would sign in every time I used the bike I'd be able to keep track of my progress. However, I can never remember my login information so I just ride for the exercise component. When I start out I tell myself that this time I'll ride at a leisurely pace, but before I know it I'm caught up in chasing after dragons. It's a fun diversion, and made the 30 minutes pass by quickly.
At the end I was sweaty and the bike display told me my heart rate had made it into an acceptable aerobic range. Time to stop chasing dragons until the next time.