Debian will likely support 32 bit until the heat death of the universe, and Slackware probably will as well. There are also the BSDs; OpenBSD and NetBSD in particular will enjoy a long life on non-x64 hardware.
I've had excellent results running OpenBSD on old laptops. I have a Dell Latitude CPx (Pentium III) that is 100% supported and runs very fast (relatively speaking) under that OS. I ran it on a Latitude D400 and D620 as well until I gave those machines away (I'm a bit of a Dell collector if you can't tell), and it works fairly well on an Acer Aspire One netbook I keep for when we go camping and my wife wants to have a machine to write her book reviews.
With OpenBSD, my experience has been generally good. On some laptops it just works by default, on others you have to configure it a bit and it will work fine after that. Here's the relevant man page: