I believe smbmount is only supported on linux,
Actually, mounting from SMB servers is now supported on FreeBSD and MacOS X (although perhaps under a different name in MacOS X); FreeBSD 4.4 has smbfs in the kernel, and a command to mount SMB file systems in the "net/smbfs" port in the ports collection, and MacOS X 10.1 includes an SMB client file system as well.
(Perhaps there's now a non-marketing reason to call them "CIFS" servers rather than "SMB" servers, as an "SMB server" now all too often means a server for Small and Medium-size Businesses....)
as for smbmount to work your kernel has to support the smbfs filesystem. I could be wrong about this, but I don't believe there is smbfs support for the solaris kernel yet.
There's none that I know of. Perhaps it'll sneak into Solaris 9, but I wouldn't be surprised if it didn't.
I suppose somebody with sufficient ambition could port the FreeBSD one (the BSD VFS interface is probably more like the SVR4/Solaris one than is the Linux VFS interface, so it'd probably be less painful; however, the VFS interface, and the VM/etc. primitives, are still different, so neither would would, I suspect, be trivial to port).