My husband recently got the JBL Clip 3. It's super small and portable, water-resistant, has a clip that you can attach to your bag or even your bike, and it packs some punch given its size. He got it in the recommendation of a friend, who also loves his.
I recently picked up a Tribit StormBox Micro that I’m really happy with. It has a silicone strap to easily attach to bike handlebars, which is great for listening to tunes on a ride! It’s waterproof, easy to use, fits in a small pack pocket and puts out a pretty great sound. It also can be paired with a second tribit to get full stereo sound.
We have a couple of Oontx triangle speakers (mentioned above) that we use everywhere. Great sound, great charge life, and easy to toss into a bag to take with us. We actually use one of these as our primary sound system in an older truck as well.