I am migrating from a Dreamweaver forced working environment to a free-of-choice one. That said I must say I was rather enthusiastic about being able to use Dreamweaver PDT.
There is something in Eclipse (at least Helios) for that. It's called Remote Server Explorer(RSE). You may need to install the run-time package using 'Install New Software' => General Purpose Tools.
You should then be able to create a new project (General), but instead of leaving the default location, you can customize the location and select the RSE file system. Define a new connection or use an existing one to your (s)ftp server.
This does not work with the PHP Project type (Eclipse PDT), because for some reason, you don't get the option to choose another file system. In these projects, you can do a similar approach, defining each file to be on a remote server (New => General => File) and then use 'link to file in the file system' setting. But it's a pita; you need to browse to the location for each file you add.
I've looked for hours for decent alternatives. The aptana plugin is a little buggy I found. Sure you can use scripts and all ... I guess most Eclipse devs don't really need this feature.
I finally decided to use Netbeans. It's decent, free, lightweight and it has about everything for PHP developing and debugging. Other languages too by the way, but I did not try them. It stopped me from losing time.
cheers