Roku LT $39

[Kaido]

http://www.amazon.com/dp/B008R7EVE4

This is the 720p Wifi-only model. It doesn't have a USB port or the motion controller for playing games, but it's perfect for older TV's or if you just need a cheap streamer. Some notable channels:

Netflix
Hulu Plus
Plex
Pandora
Vudu
Amazon Instant Video

More channels here:

http://www.roku.com/channels#!now-playing

I believe the only major channel it's lacking is Youtube. Plex is awesome for local streaming (via transcoding); you can use the Plex Media Server to manage your video files:

http://plexapp.com/roku/

Vudu is pretty awesome; basically HD pay-per-view, and sometimes the movies are still in theaters, which is really nice. I've had a good experience using Vudu for movie nights. This is a great little box for $39 and is really family-friendly. Would highly recommend it. Picked up a couple for my in-laws!

 

[JerYnkFan]

I've got one of these for a non-1080p TV and it works awesome.

 

[jhansman]

I have one in my BR and the thing is awesome. Plex streaming alone makes it worth the price.