You can use sshfs on MacFUSE that allows you to mount (as a "local" drive) any dierctory you can access to via ssh/sftp.
First you need to install MacFUSE (that is a port of FUSE [http://fuse.sourceforge.net/] for Mac OSX), you can get if from
http://code.google.com/p/macfuse/
it is a standard OS X software package that you can insatll by simply double click-ing on it.
Then you need to download sshfs (the piece of software that puts FUSE in relation with ssh)
http://code.google.com/p/macfuse/wiki/MACFUSE_FS_SSHFS
pick among
sshfs-static-leopard.gz
sshfs-static-tiger.gz
according to the version of your OS. Then gunzip it and put it in your path (open a terminal in the place where you downloaded it, then do something like
gunzio sshfs-static*gz
sudo cp sshfs-* /usr/local/bin/sshfs
sudo chmod a+rx /usr/local/bin/sshfs
don't worry if the gunzip step returns an error, it can be that your browser already decompressed it).
Now, open a terminal and do
mkdir local_mount_point
sshfs user@host:folder local_mount_point
and you'll be able to access the contents of "folder" on the "host" in the local folder named "local_mount_point" (of course, you can name it as you please). Hence, a simple
mate local_mount_point/filename
will do.
Of course, you need to install the software only once, and then you can connect (mount) as meny times you want!
BTW, TextWrangler allows to do this without installing extra software (it can save/open files via ssh on remote hosts natively).