I'd quite like something like this for my mobile http://people.interaction-ivrea.it/s.blyth/mysocialfabric/design.html
As for answering the actual question, everything is done on my mobile phone, business cards and facebook. Everyone I know well (close friends, housemates etc) are on my mobile. All my aquaintances from university I keep touch with on facebook. Facebook reminds me of birthdays and tells me what their up to in my news feed. Finally I keep all my business contacts in piles of business cards on my desk. One pile for archive, one for people I need to contact soon and one for people I'm awaiting response from. I can even easily tag people by writing metadata on the back of the card.
The mysocialfabric idea is interesting, the only problem I see with it is that there is a significant barrier towards adding somebody as a contact (you have to configure an avatar for them - what if you have never met them in person and don't know what they look like?) and I don't see how it scales (what does the screen look like when you have 200 contacts) especially on a mobile. Thanks for the answer, thats an interesting way to do it.
As for answering the actual question, everything is done on my mobile phone, business cards and facebook. Everyone I know well (close friends, housemates etc) are on my mobile. All my aquaintances from university I keep touch with on facebook. Facebook reminds me of birthdays and tells me what their up to in my news feed. Finally I keep all my business contacts in piles of business cards on my desk. One pile for archive, one for people I need to contact soon and one for people I'm awaiting response from. I can even easily tag people by writing metadata on the back of the card.