Commercial Firewalls
-----------------------------
Checkpoint UTM1 - $$$$$
Cisco PIX - $$$
Open Source Based Security appliances
--------------------------------------
Fortigate -
http://www.fortinet.com/products/fortigate/
Astaro has appliances
http://www.astaro.com/our_products/product_overview
Untangle can be purchased as an appliance
http://wiki.untangle.com/index.php/Hardware_Vendors
I've used all the security devices listed above, except for the Astaro... Checkpoint is by far the most expensive (but it is a very NICE firewall),
Don't discount the open source based appliance solutions though, those appliances work well and are far more cost effective. some are available a s software only which you can load on your own hardware to test, or use in production..