[xCathedra]

The real issue is that just over a century ago we lost a 2nd person plural pronoun and haven't really found a good subsitute since. When "you" took over for "thou" as the 2nd person singular pronoun we never replaced the original use of "you" with anything. So "guys", "y'all", "youse" are all attempts to fill the gap.

[antihero]

Folks kinda works. I usually use "guys" when addressing people, but when being extra sensitive (eg, if I'm addressing a bunch of MTF trans girls), I'll be careful and use "folks".

To make a list, for things that I use in a "Hey ___, ..." context, with varying levels of casual:

    - Guys  
    - Folks
    - People 
    - You lot
    - Motherfuckers/jerks (other insulting term that's obviously not meant in earnest)
    - Mateys
    - Chaps (debatably gender biased)
    - Team (or other factual statement e.g. colleagues)
    - Everyone
    - Dudes (also debatably gender biased, but depends on how well people know you. I call everyone dude, I am probably immature)
    - Reprobates/scallywags/some other sort of old world sounding term.

[jnevill]

Yep. "Folks". I use it in all of my communications to my group (I am not the manager). I've tried others: "Guys" is clearly gender specific, "Ya'll" is pretty informal (although I use it on occasion), "Team" is barf-o-rama.

"Folks" works well. It's reasonably formal but not gross and, best yet, its inclusive.

[BrandoElFollito]

HN is a fantastic resource for non - native English speakers. "barf-o-rama" added to dictionary.