I searched probably 20 different apps on how to use my android phone to control my computer over wifi with very little luck. Finally I found a free app that didn't charge for the server on my PC.
What you'll need,
Droid 2.0 cell phone
Wifi capabilities on your computer
Internet (not completely needed since you can d/l everything on your phones internet, but makes it alot easier)
Step 1: Cell Phone App
You can find the remotedroid app in the market or just scan this QR code.
Step 2: Download the Server App to Your Computer
Get the server app off www.remotedroid.net.
I also needed to get the java SE runtime environment installed on my system, both are available from links from the remote droid site but I included a QR just in case.
Step 3: Connect
When you start the server on your computer it will tell you the IP to type into your phone so they can connect. This is about the most difficult part of this instructable.
Remember that if you close the server window, you will no longer be able to control your computer with your phone.
Have fun with it!