Making a header that looks good on a Blip.tv show page is creatively difficult for me but the actual task isn't that bad. I've been rumbling through the header graphic tutorials on YouTube.
That is always an adventure. There is a group of people that just want to show you how to do a skill. Without sound. Moving at the speed of light. Eh, yeah. Not for me.
This video from Alphaejm is short and to the point:
Many of the tutorials use Photoshop but almost any photo imaging program has the same controls. For text and photo instructions visit Paul Stamatiou's tutorial How to Make A Header Graphic
If you don't have Photoshop that is ok. There are free alternatives like Paint.NET for PC users and Gimpshop for Mac, Linux and PC users.
Update 10/11/2012: The company Aviary.com has decided to change business focus to mobile applications. They have closed their photo, music and illustration web sites.
Update 08/08/2014 A viable and free alternative is Canva which has Twitter, Facebook and other types of header graphics.
You don't have to buy a header graphics program or affiliate marketing tools. The task is simple enough that you don't need to pay for limited function software.