Been using GRNET's ViMA service a lot lately and sometimes it happens while using a vm's console via VNC that I need to input a unicode character in a file. The VNC viewer applet that is provided, as well as any vncviewer I've tried can't seem to manage inputing these characters directly via the keyboard. Here's how I do it:

1. Install Vim on the vm with apt-get, yum or whatever

2. Localy find the unicode codepoint of the desired character:

   echo "Ψ" | iconv -f utf-8 -t iso8859-1 --unicode-subst="<U+%04X>"

   In this case it prints <U+03A8>

3. Open the file you want to input into on the vm with vim.
4. In input mode, type Control-V, u, and the four hexadecimal digits (i.e. 0,3,A and 8)
5. Viola!