I wrote a post in my blog about this subject, if anyone interested in reading it: http://neurogamerg.com/home/m/17685917/tag/%20Guild%20Website
I'll post what I wrote about getting people involved on guild websites:
a) Constantly promote your website address in guild chat and in voice chat.
b) Remind people of the many uses of a guild website.
c) Get your guild leader and other officers to lead by example and to be the first and foremost people using the website. THIS IS REALLY IMPORTANT! You need people to lead by example!
d) Post information on the website that can't be found elsewhere, such as your voice chat information.
e) Offer incentives for website use (i.e., DKP, mini contests and giveaways, etc.).
f) Post interesting things on the website, like guild videos and useful guides.
g) Make interesting threads on the guild forums, like posting games and get-to-know-you threads.
h) Keep the website up-to-date and maybe post interesting game news on the front page that can't be found on the game's website.
i) Make it a requirement for new recruits to sign up on the website.
j) Don't give up. If your guildmates have never used a guild website before, getting them to do so can be very difficult. You CAN make it work, though, so just be adamant and positive!
k) Do a little guilt-tripping and remind them of how freakin' long it took you to make your website look spectacular.