I like my Schiit Fulla. Nothing fancy, but it does the trick on my work computer.
Needles & Grooves
Goatfish
duke86fan
so it just connects to my USB no problems?
Goatfish
Yep! Super easy.
debianlinux
I use a Topping D10 and a ODAC. I prefer the D10 for various reasons.
Joe Mac
If you want something really portable with good reviews the audioquest dragonfly is literally a usb dac that is a dongle.