I access a sever over ssh on which I run vim for editing files. When I try to yank text from vim into an editor locally on my mac (lion) either with y OR "+y it does not work. I end up with the text I copied last locally. It does work if I just use p within vim alright.
To expand on Ray's answer…
When you are using Vim on a remote server via SSH, everything you do in Vim is done on the remote server. The remote server and the remote Vim that you are running on it have zero practical knowledge of your local computer and its system clipboard.
Because of that, y will never put the yanked text in your local clipboard.
In order to copy a chunk of text from the remote Vim to your local machine's clipboard you have three options:
Select the text with your mouse and hit Cmd+C like in any Mac OS X application.
Obviously, it seems to be the easiest but it has at least three limitations:
It is limited to the current screen. If the text you want to yank is not displayed entirely you won't be able to copy all of it.
It doesn't play well with set mouse=a. With this option, any attempt to select something with the mouse will result in a visual mode selection which can't be copied with Cmd+C. As a workaround, you can use Alt+mouse to select the text without entering visual mode or simply remove this setting from your remote ~/.vimrc.
Line numbers are copied as well.
Put the yanked text in a temporary file, scp it to your local machine and use pbcopy to put it in your system clipboard.
This solution seems to be a little convoluted but it works (and the problem itself is also a little bit convoluted). Over the years I've seen a lot of different implementations ranging from simple one liners to client/server setups. Here is one, feel free to google around for others.
Use X-forwarding to connect your local clipboard to the remote clipboard if available.