Last time, I had dog halos, like this and flashing collar tags, like this. The halos were quite cheap and longlasting, but the problem with them is that they are a standard size and cannot be shortened, which means that if you have sighthounds with foolishly long necks, it's rather easy for them to slide the halo off.
I like the dogs to wear different coloured lights so that if I let them off lead somewhere I can see which is which in the distance, and the halos only seem to be available in one colour now (they used to be several colours available. I wonder what changed).
The flashing collar light things are quite bright, and they come with impressive numbers of spare batteries which make you think 'oooh, these must last Aaaaages!'. Unfortunately, being dangled around the neck of a dog in all weathers doesn't seem to do much for the LEDs inside the lights : one of mine now has only one tiny red LED left, and the other has one white and one blue one, so they are quite dim, even though they are only on their first set of batteries.
So, I bought a pair of Polybrite LED collars on ebay : a green one with shamrocks for Mollydog (because she is Irish, of course!) and a yellow one with shooting stars for Az, because I thought yellow would go with his new red coats. They are quite good and bright : I have them set to flash, to conserve the battery.
I wish though that I had bought a large size one for Mollydog. Although a greyhound is a large dog, they have tiny necks (Az's tag collar was labelled 'yorkshire terrier!' so I tend to get ones that are on the small side, as big dog collars swamp them. However, if the small green collar is 'up to 16"' then Mollydog is an Otterhound. 14 and a half, maybe! It just about fits her, but there is a lot of the black tape showing, it would have been better to get one with a longer glowing bit, I think.
While I was at it, I also got a pair of 'Nite Ize' LED keyrings : a red one for Az, to go with his coat, and a white one for Molls, to contrast with the glowing green collar. They are VERY bright: it looks like the hounds have their own torches when we go out in them. I am a little dubious about how long they will last, being so bright, but we'll see.
I bit the bullet yesterday and cancelled Mollydog's medical insurance. I have joined Dog's Trust for £20 instead, and have their third party liability policy.