I've been gone for a few years and wanted to know what are the active clan and singles leagues? Is there still a good amount of people playing and competing?

maybe this can help you, it's from the ESL (electronic Sports League)
http://www.esl.eu/eu/wa/news/120399/

There's a list here:

http://worms2d.info/Community#League.2C_tournament_and_contest_sites

There's a list here:

http://worms2d.info/Community#League.2C_tournament_and_contest_sites
Hey CyberShadow, is it possible for the ESL (Electronic Sports League, http://www.esl.eu/eu/wa/ ) to get listed there too? Running currently a 1on1 League (several schemes) and hosting cups/tourneys about every 1 or 2 weeks. would be nice ;)

WKB is a wiki, anyone can edit it...

The most active league at Worms at the moment is TUS (even clan league is getting active here again)! The league offers single ladder, clan ladder and a free/misc ladder. There are plenty of cup`s hosted with a great variation of schemes. Here you`ll also find quite a few familiar faces around, I`m sure :)