Browser Add-ons
Bookmarklets (no installation, just drag-and-drop, available for all browsers)
Diigolet, bookmark, highlight, sticky note, share. Recommended for new users Simple Bookmarklet, nothing but bookmark. Read Later, mark a link to read later, and close the tab.
Extensions/Web Apps (easy installation)
Web Highlighter on Chrome, bookmark, highlight, sticky note, share. Recommended for new users Diigo Toolbar, best for power users, avaliable on IE, Firefox Awesome Screenshot, available on Chrome, Firefox, Safari Quick Note, available on Chrome, Firefox Read Later Fast, available on Chrome, Firefox
Mobile and Desktop Apps
Diigo iPad, access my library and add notes. Diigo Browser for iPad, the best browser on iPad. Bookmark to Diigo with annotation and offline reading. Diigo iPhone, access my library and read offline. Diigo Android, access my library and add notes. Readict, news reader on iPad; anntate to Diigo. Quick Note on Mac, take quick note on Mac. Syncing to Diigo coming later.
Web Services
Import bookmarks, from browser, from Delicious, from Google Notebooks. Export your library. Diigo API Send to Blog, publish annotations as blog posts easily. Tagrolls, show your tag cloud on blog. Enhanced Linkrolls, show your bookmarks and annotations on blog. "Add to Diigo" Widget Save to delicious, automatically cross-post to your delicious account. Auto blog post, automatically post your bookmarks to blog, weekly or daily. Save Favorite Tweets, automatically save your favorite tweets to Diigo.