I recently switched to historious after seeing it here on HackerNews, and I've been very happy with it so far. It's a great bookmarking service; I'm surprised it hasn't received more attention with the debacle going on at Delicious.

And there's http://www.diigo.com/learn_more which allows you to annotate and add comments on the pages you bookmark and search only the annotations (or the full text if you want). They archive the pages you read as both HTML and as an image and have support for iOS and Android.

I started to use historio.us a few weeks ago when mentioned on here and since then I've upgraded to the paid version. It really is simple to use and its really useful. To be honest I've not used any others, but for someone who used to drag and drop useful sites to my desktop this has been great.