Honestly I like the three that Elizabeth answered.
I think #2 could get derivative. Also, elizabeth's answer was so elegant and all-encompassing, it'd be really hard to top. But maybe we could consider keeping the first and last, just for this time or for a while, but changing the 2nd one each time while keeping it Hubski-themed. For instance, what is a memorable conversation you had on Hubski/what have you seen on Hubski that sticks with you? what is your favorite part of Hubski secret Hubski hacks I don't know, spitballing here.
Dude... get out of our head. We had already decided that we would like to have the last question always be the same. "What's your message?" The first question we wanted to be variable and then the second question something that is related to Hubski. So, that said, I guess its the first question we are looking for help with. Though, I'm not opposed to keeping it "what are you working on?" -It's a great question and it gets right to the heart of what many people care about most, their pursuits.
There's the old standby of what people love to talk about: FORD Family, Occupation, Recreation, Dreams. If you stick to open ended questions on those topics you can usually get people to talk about themselves for a while. What are you working on cuts right to occupation but can be interpreted by the interviewee as recreation or dreams even. It's probably a pretty good question, but as there are more interviewees, how the question is answered by others is likely to be mimicked and lose its open-endedness.
You could ask people to tell a story about something that has happened to them recently that is a good representation of their life/an area of their life at the moment. That sounds like a tall order, but it's not, really. Or you could ask "what is something you don't think most people on Hubski know about you?" (I am left-handed, can juggle, and am very good at reading Tarot cards - just off the top of my head!) I like variations on "what is your current plan/project/goal/etc" because they are open-ended but with varying the noun you can invoke different perspectives/connotations. Like a goal might be different from a plan as different from a project. "What is your current conflict?"