#1 - AMAZON PRIME
With Amazon Prime you will pay from $1.99 or more to watch a movie online. Ive tested this out on Ubuntu and it works nicely. If I had time, this is what I would use to rent movies online.
#2 - HULU / HULU PLUS
Hulu works pretty good on Ubuntu, they even have a DEB package to install. Hulu is free for a bunch of content, but Hulu Plus costs $7.99 per month if you want to access archived shows, and some of the fresh new content.
#3 - CRACKLE.COM
Lots of movies & tv shows here. Not the best, but there are some gems in the rough.
#4 - YOUTUBE
Yes, there are movies and tv shows on youtube. Sometimes it can be annoying when a movie or show is broken up into 20 parts, but what do you want for free?
#5 - PESKY STREAMING MOVIE WEBSITES WITH QUESTIONABLE ADS
Im not going to name websites, but you may know of the streaming movie websites with questionable ads, multiple pop up ads, nekkid photos, etc. There are several of these types of websites that make it easy to watch streaming movies, many of them still in the theaters. You can usually find the latest online streaming movie sites by doing a google search on "watch movies online" or something to that effect. I'll probably go to hell for posting this idea :) But... its an option, especially if you want to watch Green Lantern in Spanish with Russian subtitles.
#6 - VODO.NET
Independent movies and short films here. Worth a look since its free.
Other options that dont yet work on Ubuntu...
They have a Boxee app, but it doesnt work in Ubuntu. Their movies look pricey at $4 to $5 each for a 24 hour online rental. Vudu is owned by Walmart. Walmart is known for doing things cheaper, so keep an eye on them.
I didnt bother testing as their movies state "plays on Windows computers as a download". if you have any experience or further knowledge of CinemaNow on Ubuntu, please post a comment. CinemaNow is run by Roxio & Best Buy.
Also has online on demand movies. Again looks pricey and wont work in Ubuntu. Looks like a decent selection of movies for online daily rental or for downloadable purchase.
Here are two MORE options that definitely dont work on Ubuntu!
If you have Redbox near you, this is an easy cure for Netflix. $1 rentals for a 24 hour period. DVDs are your only option with no online streaming yet. There are plans for online streaming and whether or not it would work in Ubuntu is anyones guess right now. Redbox is owned by McDonalds.
Yes, the library. Get yourself a free library card and start renting those how-to magic trick DVD tutorials. In no time you will forget all about Netflix.