Try Postcrossing! The premise of this free website is pretty straight forward, “send a postcard and receive a postcard back from a random person somewhere in the world!”. You register on the website, say a little bit about yourself and what kind of postcards you like and then enter your postal address (no worries, it is not visible to the public), and voila you are a Postcrosser now.
Once registered you can at first request up to 5 addresses at a time to send postcards to. You will not know the people the cards go to, you can also not select where they are going to. Then you select a postcard and write a unique code on it that was given to you with the address, when the postcard gets to the person they will enter the code online and your postcard will appear as “registered” (until then it will say “traveling”). After your first postcard has arrived your address will be given to some other person somewhere in the world, twist is that where the postcards come from is always a surprise. 
For every card you send you will receive one back, but never from the same user twice. The number of postcards you can send at any given time will increase once some of them have reached their destination. Also, you don’t have to check the website all the time, you will get a handy email once your cards have arrived, usually with a little thank you note from the person.
Just some fun facts, as of November 2012, Postcrossing has 347,054 members from 210 countries who have exchanged 14,110,282 postcards (currently growing by 557 postcards an hour) that have made 1,859,491 laps around the world. Pretty impressive, eh?
As said, the site is completely free well besides postage and buying postcards. I did Postcrossing once before about 4 years ago but somehow lost track 
and stopped but I started again recently because i have collected loads of postcards over the years from various travels and i decided it was time not to dwell in the past but instead start making new memories. I enjoy getting an address, reading about the person and selecting a card for them and then being excited once it arrives. I also recently got my first postcard back this time around, it was from Missouri. OK, that might not seem like the obvious tourist destination but i don’t think i knew anything about the state before and now i do know a little so it was worth it. Discovering amazing places and “meeting” people from all over the world is to me worth the 50 Euro cents it costs to post a card there. Especially now that winter is coming, you will leave your home in the dark and get back when it is dark. Finding a little surprise in the mailbox from a lovely person from somewhere in the world really makes my day..and i hope it will make yours too!
Exploring Estonia 