Really depends, on your take on "best". There's PLENTY of free portfolio hosting sites that will do different things, but many offer only 1 or 2 layouts. The basic functions of them are still all the same, upload photos and display, but it really depends on HOW you want them displayed, and that goes with the layout offered by the webhost. If you do a simple google search for: "free portfolio website", there's tons that come up. View their examples/samples, and choose the layout that best fits what you want to do. Wordpress and tumblr are always great alternatives as well. I've personally used carbonmade before, but they limit you at about 30 photos or so..
Also, if you're looking for inexpensive hosting, John offers a POTN discount on the forums. It's $4/month for hosting, and with a free wordpress layout, you can honestly get yourself a better looking portfolio for very cheap. You can also buy a domain name, which usually goes on sale on GoDaddy for $1/year.
Link to deal: https://photography-on-the.net …810&highlight=web+hosting