Theoretically, you can annotate your bookmarks, entering free-form reminders to yourself so that you can remember why you bookmarked this page or that one. I don’t know about you, but I never actually got around to doing this — it’s one of those get-to-it-later eat-your-vegetables best-practice housekeeping tasks like defragging your hard drive or squeegeeing your windshield that you know you should do but never get around to.
Until I started blogging. Blogging gave my knowledge-grazing direction and reward. Writing a blog entry about a useful and/or interesting subject forces me to extract the salient features of the link into a two- or three-sentence elevator pitch to my readers, whose decision to follow a link is predicated on my ability to convey its interestingness to them. This exercise fixes the subjects in my head the same way that taking notes at a lecture does, putting them in reliable and easily-accessible mental registers.