Best way to encode..
 

Emailing large (text) attachments over unsecured networks? Thinking either an encoder/decoder program or maybe compressing and adding a password? I know neither of those things, so if either is viable please include details.

Compression and security are two separate issues. Zip or gzip compression will work great to reduce the data size (you can expect at least a 2:1 compression ratio for most text), but zip passwords are only the most rudimentary form of security, if you are concerned with someone reading the contents. To protect the contents you would want to use something like PGP or GnuPG, but they are not known for ease of use.

If you use Thunderbird as an email client, you can install the enigmail (Enigmail - Wikipedia, the free encyclopedia) plugin which makes gnupg very easy to use.

Nice, thanks guys!

PGP isn't too difficult to use. It may take 15 minutes to maybe half an hour to set it up but most of that time will be spent RTFM. :-) And it is *totally* secure.