Since we have been working with shaders for our Graphics course in the last couple weeks, the following is a great resource for writing HLSL shaders in real-time.
Original Forum Post:
Note: Unfortunately the download link on the forum no longer works, however Tom has provided it on his website: Download Shader Editor
“The author posted a link to a youtube video displaying it. It’s really nice, it gives you error updates in realtime, and lets you load an image, and change it around to your needing, and you can set custom variables (and set them to increment on a time interval) to use in the shader.”