Here's a great pickling recipe that I did several weekend. It's from one of my favourite new cookbooks: A New Turn to the South by Hugh Acheson. I have pulled a jar of these pickles out on several occasions and they are amazing! They're awesome on their own or even in a sandwich.

Directions

Core and thinly slice tomatoes. (1/4" thick)
Process jars. I used 500ml wide mouth mason jars. Here are good instructions for preparing the jars.
Stack sliced tomatoes in processed jars. Make sure to leave enough room at the top for the brine.
Ladle hot brine into jars. Leave about 1/2" of space at the top of the jar. See the brine recipe below.
Process filled jars in boiling water for 8 minutes.

BRINE (for 6 500ml jars)

2C sugar
2 Tsp mustard seed
2 Tsp fennel seed
1 Tsp hot smoked paprika
pinch of red pepper flakes
2 2/3 C cider vinegar
1 1/3 C water

Bring all ingredient to a boil in a pot. Simmer for 2 minutes.