One of the best resources to understand Synesthesia - especially if you are a synesthete is to join the Synesthesia List run by Sean Day in the USA.
The list has researchers, artists, parents, synesthetes and others, raising issues, discussing synesthesia types. The list is moderated by Sean so there is really no junk email.
Of course, youtube has several videos now and Amazon sells quite a few books too. You can find these listed in the research area of this site under the research Menu link and by using the tabs called informative videos and informative books. The creative content from synesthetes is under the Create menu.
There is also a terrific toolkit for parents and kids with synesthesia.
If you want to stay current - please consider signing up to our newsletter. I publish it once a fortnight and it goes to subscribers on my list.
Happy reading! (or watching)