I make sure to send postcards to a few like-minded friends whenever I travel. The thrill of a postcard through your letter box is more exciting than 1 new message in your inbox.
In Venice, being a busy tourist destination, they have some absolute crackers of postcards. From the tasteless to the tasteful, here's some I've picked up and sent on their merry way across the globe.
Prices of postcards, like every souvenir, vary in Venice. Near the Accademia Bridge and around Rialto I have seen single postcards sell for 80c - €1, when there are similar ones for half the price in places not so close to the hotspots, for about 30c - 50c. You can often buy '10 for X' for a better deal. Stamps can be bought in Tobacconists (shops with the blue sign and a prominent white T), a postcard to Europe costs 75c. The postboxes are very non-descript. They are burgundy, with two separate mail slots for City destinations/All other destinations.
If you're interested in penpalling, the art of letter writing, check these out:
The Hairpin: PinPals
The Letter Writers Alliance