You should also check out
this thread from over a year ago. InDesign Template sharing! I don't know if they're still up, though - so far I've just designed from scratch. I'm sure someone could start adding again if they wanted.
FYI - The way I've found to be the best for using InDesign is to set up a standard layout that I use - for me, it's 20x10. I have it set up with all the Object Styles I use, and I make sure the color space and transparency blend space are they way I need (srgb and document rgb, respectively). On my master, I drag in guides where I want to always have them and put them on their own layer, so I can make them disappear if I want (they'll also disappear by hitting w). I then apply the master to all pages, and now guides show up on every page. When I start a new design, I just open this file, save as in my client's folder with that client's name, and I'm good to go.
I'm still kind of slow, though! Actually putting elements on the page goes quick, but I'm horribly slow at deciding how to design each spread. I'd probably be faster starting with a template!