There are far more intelligent articles on the internet about the uses of essential oils (and I would strongly recommend that you do some research before creating your own concoctions, essential oils are pretty potent).
Here are some of my ideas and uses:
I like a mixture of tea tree and lavender to dab onto blemishes. I tend to buy lavender and tea tree whenever I see them at a reasonable price, although I do prefer organic for lavender. Mix these with an oil such as Jojoba or almond before applying to your skin.
Lemon or Lemon Eucalyptus is wonderful for cleaning (mixed with cheap white wine vinegar) and adding to conditioner sprays/body mists. It's also good for getting rid of insects in summer.
Peppermint or Spearmint blended with a little Jojoba oil is lovely on pulse points when you are stressed or have a headache. I also really want to make a D.I.Y mouthwash, but haven't quite figured out how to accomplish this yet.
For hot baths, I love Lavender or Rose, but my absolute favourite is Geranium from Neal's Yard Remedies. It's like rose, but more earthy and grounding.
In D.I.Y deodorants I like lavender and tea tree. Or Patchouli, to mimic the scent of my favourite Lush deodorant (the only thing I would buy from Lush, FYI).
For D.I.Y body mists, I like a mix of Geranium and Patchouli, which is floral but intense. Or something lemony (a lemon body mist also doubles as a lovely laundry spray). I tend to mix the essential oils with floral waters, like orange blossom and rosewater. I also use the Tisserand Rose Absolute or Lavender essential oil as a travel perfume.
I tend to buy my essential oils from Neal's Yard, but have started buying some from Holland and Barrett - although this is trial and error, as some are better quality than others. Tisserand also have some lovely essential oil blends.
I would love to hear about essential oil based recipes, please share in the comments, or Tweet me.