As a consequence of yesterday's unfortunate news that Yahoo! would appear to be dumping the online bookmarking service, Delicious, many users of that service, like myself, are looking for a good replacement.
For many, the first thought would be Diigo. However before you rush to Diigo, there are several good but lesser known alternatives that you should consider.
Pinboard
The focus of Pinboard is less on socializing, and more on speed and utility. The goals of the site, in order of priority, are to never lose data, be ridiculously fast, and offer useful features.
Pinboard's basic functions work very much like Delicious. I think that if you liked using Delicious, Pinboard will be your choice.
The unfortunate part of Pinboard is that users pay a relatively small one-time signup fee. In return, they are promised a fast, spam-free service with prompt support.
Zootool
Zootool is about collecting, organizing and sharing your favorite images, videos, documents, and links from all over the internet. The Zootool graphic interface is unique and sharing web content is easy.
Some of the accounts you can connect Zootool with are Facebook, Twitter, Tumblr, Posterous, Flickr, LinkedIn, Vimeo, and YouTube. At the time I was preparing this post, Zootool was offline because of extremely heavy import traffic.
Historius
Historious saves you time by enabling you to find webpages you saw before. Bookmark sites with a single click, then find them again by searching for any word in the content of the page.
All your bookmarks are individually indexed to create a personalized searchable database of your links. Note: The free account will import only 300 bookmarks.
Licorize
Licorize is a minimalist and fast to-do manager that you can feed with your bookmarks and web updates. With Licorize, turn web page bookmarking and status updates into projects, ideas, and collaborative teams.
Licorize can import your bookmarks from Delicious as well as from Instapaper, Firefox, Chrome, Safari, Opera, and Internet Explorer. You can also synch them with Read It Later. By enabling DropBox integration the user it will be capable of sharing strips with project colleagues.
Migrating from Delicious
These services will all import your Delicious bookmarks from an HTML file. You must first export your bookmarks from Delicious as an HTML file, and then upload it.
Adding Bookmarks
You can easily add bookmarks to any of these with bookmarklets and/or browser extensions.
Google Bookmarks has been around for a long time and is easy to use, however, there doesn't seem to be an easy way to import your Delicious bookmarks without installing the Google toolbar in Firefox.