I love this spa in a jar idea. You could add a fun label with ribbon. Some ideas for the contents could be mini lotions, soaps, foot scrubs etc. Lip balms, nail varnish, face masks, mini bath bombs, bath bags, soft flannel, and some yummy chocolates and sachet of hot chocolate.
How about this housewarming gift jar found on this blog. You could add some hand soap, labels, dish towels, chocolate, dishwashing sponges, small jar of jam, cupcake liners, recipe, paper clips, sweets, measuring tape, magnets, superglue.
Lots of ideas for a baby shower gift jar. I love this one by Marythekaytheblog You could add baby wash cloths, dummy, socks, booties, mittens, rubber duck, mini baby shampoo, lotion, baby vest,.
The easiest jar for me to put together would be a jar for a fellow crafter. I found this one on Prettify Your Life You could add ribbon, mini stamps, brads, pens, inks, cut out shapes, pins, flowers, embroidery thread, buttons, beads, charm, jewels, fabric...