The easiest way is to use a track archive.
I’m not sure what version of Cubase this was introduced in, but it is there in C6.
Simly select every track you want to share in the project, and go to
“File-Export-Selected Tracks” and follow the prompts (you will want to copy the media, as opposed to referencing it).
This will create a Steinberg XML file that can be imported into any version of Cubase - or Nuendo - that supports this.
If you also have either SSL ProConvert, or Suite Spot Studios AA Translator, you can also convert the sessions from almost any ther DAW to a Steinberg XML file - or Vide-Versa - for sharing with others.
Have you tried DropBox at all? You can get an initial limit of 2Gb for free, or pay $10/month for a 50Gb limit.
If you RAR the audio files then you will get a lot more into the allowed space as well. Just (for safety’s sake) do not use DropBox on your working DAW if you have a secondary system available.