I use the Scrap Book extension in Firefox to archive promising websites for reading more closely when I have more time. I also use it to store websites that are definitely related to specific projects. This keeps my project reference material from getting lost in my general bookmarks.
I also sometimes save interesting websites in Furl.
This has worked well so far. I have an archive of interesting websites when I have time to look at them, I don't feel I've missed any potentially wonderful information, but the sites are easy to sort through, delete, annotate, etc. at my leisure.