Conundrum, for home, WRT54GL with third party software, can do a lot and has a lot of real-router/real-firewall features at a SOHO price.
For small to medium sized businesses, OpenBSD/pf if the company's open minded, or ISR/IOS if they're not. The cisco solution is buggy as hell but conservative business types will buy cisco. I also do a lot with NetScreen firewalls, they have better performance and lower cost vs. an ISR, but they're just as buggy, much more painful to administer, and a harder vendor to convince business folks to buy from. There are a lot of new products in this space, such as the Juniper security routers and the cisco ASA, that look interesting but I haven't had an excuse to play with yet.
For large businesses, you're typically layering more specialized devices, getting some high-performance firewalls, maybe some load balances, some IDSs, spam filters, etc. Then it's not easy to recommend, it really depends on needs and budget.
For Windows software firewall, I've been pushing folks to use Sunbelt Kerio. It's okay, not great, not horrible, but I haven't had any problems with it. I've had a lot of problems with ZoneAlarm updates trashing Windows to the point where a reinstall is required, and in my experience Symantec products also have a habit of trashing everything beyond repair.