I work in a marketing team that is scattered across the globe, literally.  I use greeting cards to thank people for their help; encourage people when they are feeling low;  recognize milestones in their career; or congratulate them on a birthday, anniversary, wedding or birth. There are so many reasons to send colleagues cards and then of course you can send one just because.

You will find if you make this a regular practice you will have better relations and get more done as a team. It is so simple to do, yet the good effects are quite profound.