WA7BNM maintains a ham radio contesting web site which is probably the key reference for what contests are going on. http://www.hornucopia.com/contestcal is the main site but I typically view http://www.hornucopia.com/contestcal/weeklycont.php for the upcoming week. A change that WA7BNM has recently implemented shows a graphical representation of when the contest is active using UTC. It gives a quick overview of what contests are active during what times.
It also looks like there’s some customization (stored locally on the computer you use) for which contests to view if you wanted to filter out contests you weren’t interested in. Thanks to WA7BNM for maintaining a web site with great information I visit multiple times a week.