Keeping in touch with people has become a paradox.
On one hand we have never had so many ways to communicate, on the other we have never had (or appeared to have) so little time to make contact.
A top tip from Merlin Mann on his podcast Back to Work with Dan Benjamin is to make a list of 6 people you want to improve your relationships with (excluding close friends, colleagues and family who hopefully you already see enough of). Maybe these are old friends, 'like minds' or just people that inspire you. Maybe you could offer skills swaps with them - improving the quality of your life, personally and professionally, and sharing or honing your talent at the same time. Anyhow once you have your list of 6 ready - call, email or text them and arrange meetings with them once every 6 weeks. With this amount of time between get togethers you will always have new things to talk about and yet they'll be close enough to flourish. Who knows these encounters could lead to what Ian Sanders, writing in the FT, calls 'side-projects'? Interesting projects that stimulate you, complement or feed into your existing work and life commitments without overloading them.
So every week of the year you get to meet someone interesting. And with some forward scheduling your '6 every 6' programme can just keep rolling on with the minimum of hassle.