I'm not too familiar with the issue but Solaris PC NetLink is free and does some neat things:
Unfortunately, it appears that one of the things it does *not* do is let you mount CIFS on Solaris. It may let you mount CIFS *from* Solaris - which is also what Samba does - but that's another matter.
Neither Solaris PC NetLink nor Samba provide what the original poster wanted; they're for people who want to make their UNIX box (or VMS box, in the case of Samba) a CIFS *server*, not a CIFS *client*. The original poster wanted to make his Solaris box a CIFS client, not a CIFS server.
Samba does provide "smbclient", but that's a command-line SMB client with a user interface like that of the "ftp" command, not a VFS that allows you to transparently access file systems on CIFS servers the way the Solaris NFS client VFS lets you transparently access file systems on NFS servers.
Sharity, from Objective Development:
is, I suspect, a "user-mode file system" (i.e., an NFS server, perhaps running on a port other than the standard 2049) that acts as an NFS client; this is the closest thing to a VFS that runs in user mode, and it has the advantage that it can run on a large number of OSes. (It's somewhat amusing, though, that the Sharity page:
http://www.obdev.at/products/sharity/index.html
specifically cites MacOS X, Linux, and FreeBSD, given that those are the three UNIXes I know of that have a *native* SMB client VFS and that therefore, in their current versions, don't *need* Sharity...).
Sharity-Light:
http://www.obdev.at/products/sharity-light/index.html
is a "user-mode file system" of that sort, based on an "outdated version of smbfs for Linux"; it's free, but, as they note, it's based on an older version, and they're not doing any enhancements to it.