NTLM authentication on Macs???

I've got a few hundred Macs in an environment of about 45,000 PCs, so we're a bit Windows-centric. Now, the Mac users are always bummed because a lot of our web-enabled applications use NTLM authentication which, as far as I know, excludes the Mac users. Is there any way for Macs to join in on the fun? Most of our stuff runs on Win 2000 boxes, but I think that there's somethng about 2003 that might make this work (?), so maybe if all else fails we could upgrade some of the more indemand boxes? So, anyone know if Macs can do NTLM natively or if there's some product we could buy? Thanks.