So this one was a given for me from the day I started planning out these posts. Māra, aka Māre, Mārīte, Mārša, Māršava, and, if your polytheism is a little softer, Maržanna and Moréna, is a goddess that I have had the pleasure of working with for more than ten years. I was introduced to her originally by an ex, and while I have re-evaluated many things from that relationship, Mara made it clear that she was going nowhere.
While the Latvian god Dievs is the sort of sky-father who's busy with souls and other such big-picture things, Mara is the lady who keeps things running smoothly for us down here on the earth. She's a patron of the marketplace, of children and animals, and in general she is interested in seeing her children comfortable for while we live our mortal lives. Since I don't currently have children or livestock, I mostly relate to her as an economic goddess.
She most likely is tied to the Proto-Indo-European *mer, which means to die. While the Slavic Marzanna is a much more obviously death-related goddess, the Latvian Mara is not without cthonic attributes - not only is she sometimes considered to be the earth itself, with all it's attendant harvest and burial imagery, but she is specifically noted as the deity who takes care of the body after death (as opposed to Dievs, who concerns himself with the soul).
Mara is probably the goddess I have the most interaction with on a day-to-day basis. She gets offerings in all sorts of forms - foreign or historic coins, along with tokens and other coin-like items, precious stones, and candles, home-baked bread, and the like. My first pay stub from my current job still sits on her altar, a thank-you for her help in securing it. Her statue is actually a figure of the Catholic Mary, which I think is not inappropriate - her festival was celebrated around the time of the Assumption, in August. She shares the space with her sister Laima and with Ganesha (both because of his relationship with Laxshmi and because his portfolio is relevant to hers
She is a very down-to-earth goddess. (Pun not intended.) She asks things of me, but she expects me to use my common sense and discretion to decide when and how to do those things. She concerns herself with the everyday lives and needs of her worshippers, answering prayers for jobs, animals, and those times when you're just not quite sure how you're going to make it until next payday. She encourages setting aside for a rainy day, but she also knows floods happen.
Put simply, Mara has never let me down. I've been scared, I've been close to giving up, but she comes through.