Three ways to stream movies to your iPhone

mSpot's new Mobile Movies service works in the iPhone's browser--no app required.

Sure, you can now download movies straight from iTunes to your iPhone, but those cost money and consume valuable storage space. Sometimes it's faster, cheaper, and more convenient to stream them, whether from your own PC, online storage, or even an on-demand service.

Here's a look at three such options for streaming the big screen to your small screen:

• Dropbox This just-released iPhone app (CNET's Harrison Hoffman has more) connects you to all the documents in your Dropbox account (including 2GB freebie accounts). So what does that have to do with movies? Simple: The app also lets you view mov, mp4, and m4v videos. Just add some from your PC to one of your Dropbox folders, then fire up the app. Presto: You're watching movies, and you don't have to leave your PC running to do it. Not bad for a solution that doesn't cost a penny.
• mSpot Mobile Movies This new service, which operates out of your browser, lets you rent movies for $4.99 apiece (less if you subscribe to a club membership). That's more than iTunes charges, but here you're getting an on-demand, download-free option--one that works over EDGE, 3G, and Wi-Fi. However, mSpot's selection is very small at the moment (about 350 movies in all), with marquee titles like "The Curious Case of Benjamin Button" and "Mission: Impossible" among the few you'll recognize. But the company promises "thousands" by year's end, so this service is definitely one to watch.
• OrbLive Unlike Dropbox, which can play movies you've synced to an online account, OrbLive streams directly from your PC--which must be running in order for it to work. You also have to install and configure the Orb client for Windows, point it to the folder(s) containing your videos, and pony up $9.99 for the OrbLive app. On the plus side, it can stream a lot more than just videos: music, photos, and even live TV (if your PC has a tuner).

So, what do you think of these solutions? Obviously they're no good for watching movies on airplanes, but what about on trains? In a car? In a bar? With a cat or on a mat?

Of course, if you know of a better way to stream feature-length video to your iPhone, let's hear it!