What do you do with Business Cards

After my office / life cleanup, I found that I have 100's of business cards that I have collected over the years from clients, partners, competitors and just random people that I have crossed paths with.

My question to everyone is: What do YOU do with all the cards you collect?

Years ago I use to enter every single one into my Contacts in Outlook (via different mobile apps / direct into outlook) but found that I ended up with over 5,000 contacts, most of which I would not likely contact.  So over the years I started piling these cards up in the boxes that my Business cards came in and only entered the ones (like clients) that I knew I would need in the near future.

Quickly sorting through my current pile of cards, I sorted them into 3 separate piles:

1. People that I should be in contact with (Example: Clients & Partners)
2. People that I may contact one day (Examples: Software vendor reps)
3. People that I don't remember meeting / have no clue why I have their cards

The first group is easy to figure out what to do with, schedule time and make sure their contact info is in / up to date in my Contacts.

The second group is really where I am struggling, do I put the effort into entering these all into my Contacts in Outlook, just leave them as is for future reference, or trash them...

The third group, straight in the garbage can.