In om,
Mary composed with style:

Any tips on good window seats for kitties that are simple to install
and lightweight and nice for the cat? I expect to go to PetSmart or
elsewhere later today and I would appreciate any advice. It is a
regular sized window. Thanks!

Mine like this one: http://tinyurl.com/y06x
This online price is better than what I paid in the store for it. Too
bad I already used my free shipping promo earlier this week or I would
have added this. What I like about it is that it is held by gravity
and leverage, and a small velcro strip on the sill. I got some extra
velco from a craft store and can move the window seat to another
window to keep things interesting. A second perch would be better,
though.