I use Instapaper as well, but the things I might want to read again, I email into Evernote, and then I tag them. Evernote's full text search is really good, and will make it easier to find things later. Notebooks and tags also allow you to categorize things. When I'm researching a new technology or a product, I can clip a bunch of things into Evernote and then tag them with the tech (Chef, ElasticSearch, whatever).

Email stuff into Evernote. I do this all the time. Tax receipts get a tag for the year and get stuck in a folder called "Tax Receipts". Then at the end of the year it's easy to find them. Tweets that contain links I may want to look at later get emailed into Evernote.

If you scan documents, Evernote will OCR them and then the search makes them easy to find.

Checklists. I do checklists for quick todo lists, like travel checklists and things.

Notes. I take meeting notes, tag it with the project name, and then I can email or share them in Evernote. I also use it for lots of other notetaking tasks. Blob post drafts, funny things my kids say, etc.

With the iPhone app, I can take notes on the go or review checklists, and I also frequently take pics of things I may want to buy later.

There's a million more things you can do with it, but these are my common use cases.