I use ASP on IIS, which requires cookies for maintaining session state. I'm
looking for solutions to avoid this (I want cookieless sessions),
which also require minimal development effort to implement.

The general conensus seems to be that encoding a sessionid into
relative URLs on the site is the best method for tracking sessions
without cookies.  But I don't want to do this by hand.

The desired answer will:

1. Identify 1-3 products which accomplish this and can be purchased
online, or are free. No or minimal code re-writing is a requirement.
2. I have heard rumor of a (free?) ISAPI filter which can do this; please
find this for me.
3. If there are other options worthy of considering I'd be glad to
hear it. Remember I'm on a tight schedule and a tight budget.

Any product/software that you list needs to have an option of going
completely cookieless -- the default is probably to use cookies if
available, and URL-tracked sessions if unavailable. I specifically
need a package that lets me (optionally) specify that cookies are
NEVER to be used.

The url for a shareware ISAPI URL Rewriter is http://www.isapirewrite.com/

Alternatively, you could store the session is in hidden form fields.