Dustin Evans shows how to stream media to a RPi with AllCast:
Got my Raspberry Pi running Raspbian (http://www.raspberrypi.org/downloads) to broadcast its own access point using +Adafruit Industries tutorial (http://learn.adafruit.com/setting-up-a-raspberry-pi-as-a-wifi-access-point/overview) and this WiFi adapter they sell http://www.adafruit.com/products/1030.
Once that was all setup I installed XBMC using this guide (http://michael.gorven.za.net/raspberrypi/xbmc)
Now I can connect to my Raspberry Pi using my Galaxy S3 and send local videos to it using +Koushik Dutta ‘s #AllCast app.
Without the need for a router.
More info here.
From the Adafruit Learning System
Setting up a Raspberry Pi as a WiFi access point – Would you like to use your Pi as a WiFi router? Or maybe have it as a special filtering access point? Setting up a Pi as an access point (AP) is a bit more advanced than using it as a client, but its still only a half hour of typing to configure. If you want to, this tutorial will make it so the Pi broadcasts a WiFi service and then routes internet traffic to an Ethernet cable. Since its all Linux you can go in and update or configure it however you like. (read more)
Featured Adafruit Products
USB WiFi (802.11b/g/n) Module with Antenna for Raspberry Pi – Make your Internet of Things device cable-free by adding super WiFi. Take advantage of the Raspberry Pi and Beagle Bone’s USB port to add a low cost, but high-reliability wireless link. (read more)