I don't even know why we eat tomatoes in the winter. If any of you have read Barry Estabrook's fantastic book "Tomatoland," it'll convince you to never buy another tomato grown in Florida (or really, any commercial tomatoes at all).
That leaves us with late summer market tomatoes, and they're so much better than the tasteless, mealy, pink-fleshed things we call tomatoes in the grocery store that you'll never look back.
I put heirloom tomatoes in a salad at the wedding I catered recently and had someone talk my ear off for 10 minutes about how good the tomatoes were. "But they taste like tomatoes!" Yes, yes they do.
Varieties: Heirlooms come in a few categories: Commercial Heirlooms, Family Heirlooms (I wish my family had heirloom tomato seeds!), Created Heirlooms, and Mystery Heirlooms. The main premise of heirlooms is that the seeds have been passed down for generations, or are varieties that have occurred naturally or have been in circulation for over 50 years.
Appearance & Buying: Heirlooms can come in all kinds of colors, from flame orange to greenish to purple to bright yellow to mottled and striated. They're more delicate than store bought tomatoes, so don't squeeze them too aggressively or they'll bruise (and be careful getting them home!). Just buy tomatoes that are firm, but not rock hard, with no soft spots or bruising.
Storage: Do not, I repeat, DO NOT refrigerate your tomatoes. It ruins the flavor and texture. Store on the countertop and they should be fine for a few days.
As a reformed tomato hater turned tomato lover, I invite you to tomato week!