I found access to Mitchell and it seems even more comprehensive than the other diagnostic site I found! Don't know how this compares to Alldata but from the forum I read it seems to be just as good.
NOTE*** It seems the site works in IE only. It didn't work in Chrome for me and I didn't download other browsers to test. I confirmed it works in IE though.
Here it is: http://www.ondemand5.com/
I tried it and the login works. Even more info for working on your car!!!!!!!!!!!!!!!!
P.S. This is where I found the info for the login at if you wanted to look at it....