There are a fair number of websites out there that aim to cater to those who are looking either to improve at chess, or simply to play it or spectate it. Below is a list of some sites that serve those purposes exceptionally well.
This one’s pretty obvious. You can go there and sign up within a couple minutes and play as many live games as you want, at whatever time control you want, for free. You can also play correspondence chess, and chess 960.
Great site that lets you do as many tactics as you want for free. It also gives free access to easily searchable database of chess games. The only downside is that sometimes there can be six-month stretches between updates to the database. Nonetheless, ChessTempo is one of the most useful sites out there for beginners trying to improve.
Basically a massive database of games. It seems to be updated more frequently than ChessTempo, but its database is not as easy to sift through. Definitely worth a look though.
This is a really neat site that tracks the live ratings of all the players who are rated over 2700. There’s also an option to include all players in the Top 100. Clicking on a player’s name will show the outcomes of their most recent games and how their rating changed as a result.
This sites gives coverage of top level chess games being played in real time and is a great resource for those who don’t want to wait for the games to be uploaded to an online database. Chessdom also includes engine evaluations of most moves for all of the games it covers. If you want to watch the major tournament games as they’re being played, this is one of the best sites.
This should be enough to get you started. There are, of course, many more excellent chess resources online, and this post will be updated frequently to add them to the list.