I love this question! I bake bread a lot, and the smell of baking bread has a lot of memories for me. I grew up baking bread with my Grandma and my Mom, and they both taught me how, so when I make bread, I think of them...I still bake bread with my mom. My Grandma used to tell me stories of her childhood while baked.
I also love the smell of real vanilla, vanilla beans and vanilla paste. Yum! I cannot stint the smell (or taste) of imitation vanilla, so fake.
Fresh herbs like rosemary, mint, thyme, basil or tarragon. We grow our own herbs in our garden (many of them winter over) and whenever I want a pick me up, I go out and pick some fresh herbs and smell them. They are wonderful!
Roses smell good to me. I often have vases of fresh cut roses from our garden throughout the house in the summer.
I don't do scented candles because they give me a headache.