[Cool Tool] FTP Live
This is not a "must have" but a "good to know", as it can be pretty useful.
Have you ever been is a situation where you have to upload files to an FTP server but have no access because FTP ports are disable (at work for example) ?
So you can't use any FTP client, even the one in IE, but if you have internet access (at least port 80:web), then you can use ftplive :
With this free online service you can do FTP from your browser, without problems of firewall or ports disabled, and nothing to install.
The only concern is... will you trust a website to get your server/password combination ? you should not.... or at least change your password back home.