I've probably got a few too many buckets here that should be cleaned out, but I've found that
Instapaper is a great resource for flagging items to be read later. This benefits from pruning, but it's a very lightweight tool, I've found it less cumbersome than trying to use a
"ToRead" tag on your own del.icio.us account.
I also use Google Reader, and star items to follow up on later.
One thing that is direct from David Allen, is keeping a Read/Review folder in my bag/briefcase at all times. While Davidco sells expensive poly folders, I found
these at Staples a year and a half ago and they're great - I applied labelmaker labels to them when they first went into my bag and haven't come off since.
I'll tear out magazine or newspaper articles, or occasionally print something out, and keep it in there. Leisurely stuff, different than on-the-go reference materials (that's kept in the "Action Support" folder).
(Actually, just looked at
the DavidCo page for the poly folder link, and found that their $19 for 18 folders price is comparable to the Staples $6 for 6 folders price. I've only ever used the six, though - occasionally I'll slip a project-specific manila folder into my bag if need be. The Poly folders hold up very well to daily abuse)