I think the link posted earlier is probably as good as it gets for free dog clothes patterns. If you're decent at sewing and creative, it can easily be adjusted to create a lot of different looks.
http://www.bellaonline.com/subjects/7376.asp
On this site, there are a couple links to really basic dog coat patterns (incl. the one posted above), dog booties at the bottom, and the rest is mostly sweater patterns. It's likely not quite what you were hoping for, but perhaps it will suit someone else's needs.