If you've been waiting to check out the Nintendo Switch Online service, it's live now — as are all of the NES games that come with it, and the free 7-day trial.
To activate the trial, you'll need to make sure your Switch is updated. I had to manually push the update through the System settings — the console didn't pick it up automatically.
Once that's done, browse to your user settings page (top left of the main Switch menu). From there you'll see a tab that says "Check Membership Status in Nintendo eShop".
That will take you through to a page where you can select Membership Options for Nintendo Switch Online, after which you'll see this:
As before, it'll cost you $5.95 for a month-on-month subscription, $11.95 for three months at a time, or $29.95 for a full year. Family accounts, which support up to 8 accounts and last for a year, cost $54.95.
You can activate a 7 day trial, and subsequently disable the trial from the Pass Settings tab in your user settings. (If you forget to cancel the automatic renewal, it will renew the membership on a monthly basis.)
From there, you'll be able to download the Nintendo Entertainment System - Nintendo Switch Online software. You can launch single or local co-op games from here, and there's a button to start online play. If you don't have any friends' games to join, it'll let you launch a game of your own with an open slot so others can join. (You can lock it with a password, if you want.)
Here's a shot of Tennis going, because I picked it at random:
You can activate all of this through your Switch right now. The NES download is just over 50MB, so you might as well grab it on the work/school/uni Wi-Fi before heading home.