Check it out-- if you enjoy sidebars / panels you may like the PHP Reference panel found here: http://webtoman.com/opera/panels.php
his html colors are useful too!
there are several other useful "panels" out there as well.
http://my.opera.com/community/promote/fans/links/
(about 1/2 down the page)
Others are found through the browser (opera) itself-- just click right-click an empty area of the side panel and select "get panels".
i think everyone probably knows this one, but i'll stick it here anyway.
http://www.tntluoma.com/sidebars/
enjoy.
