How do I copy files to a Windows Share?

Unless you're looking for a permanent setup (where smbmount might be better) you want to use the smbclient solution, which acts similar to a FTP client. You connect, then cd around and put/get files.

Connect as follows:

$ smbclient //computer.domain/sharename -U domain/username
Enter domain/username's password: 
Domain=[DN] OS=[Windows Server (R) 2008 Enterprise 6002 Service Pack 2] Server=[Windows Server (R) 2008 Enterprise 6.0]
smb: \>

Check the manual page here: http://linux.die.net/man/1/smbclient

I assume that you use *NIX.

So, basically, you have to mount the share with smbmount, then just use the cp command.

Refer to this and CIFS utils

To expand a little on @onur's point - as long as you have a filesystem mounted, (almost) all normal file utilities should be usable, as at that point it just appears to *nix as a filesystem.

Samba allows you to mount windows shares using smbmount, which comes as standard with many distro's and as an option with most others.

Commands such as cp, mv etc should work just fine.