Really cool plant resource; I applaud you, just found your site through a google search for the search term "permaculture encyclopedia", your link through this site was third on the list of the results.
You ask how to spread the word, well i'm an online marketer and here are a few of my most effective tips.
I recommend you use other forums and sites (youtube, blogger, wordpress, squidoo, hubpages etc) that allow you to create your own content on, the more popular the website, the better results you will get and quicker as well.
If I were you I would do videos on youtube and in each video I would get very specific with whatever topic you choose to speak about, obviously the more detailed the better, keep your vids short so it's easy to follow and concise. The shorter the video generally speaking, the more videos you can make because it will be easier for you to produce and also because more people will find you on google or youtube (via the relativity of your title and description words) as opposed to making one long video which could be broken down into 100, catch my drift?
I hope you do great things with this site,
Keep fighting the good fight.