I don't get to the meetings that often, but any of those subjects would be great IMHO.

  While not specifically Linux related, maybe one on 3D printing would be cool?  I don't have a 3D printer myself as of yet, but a buddy of mine does, and it's pretty awesome.  It's amazing what you can create once it's 'dialed in' and you learn how to use it properly.  (IE: The proper temperatures for the hotend and bed for different filaments and how to get the plastic to stay 'stuck' to the print bed.)  And actually, there _is_ a Linux component to his printer now, lol.  We setup a Raspberry Pi running "OctoPrint" on Raspibian to not only control his printer, but it gives it an HTML interface, wireless networking, a webcam monitor and time lapse function.  It's really cool!

  Speaking of the Raspberry Pi, maybe a night about the Pi, the various models (A, B, B+ and the new A+) and some projects that use them would be of interest. 

  For instance, one of my current projects is taking a Dummy Security Camera and converting it into a real HD Wireless Security Camera by putting a Raspberry Pi A+ with a camera and Wifi inside the dummy camera.  (the A+ is quite small, so it fits quite well - all the other models won't fit without some potentially serious modifications to the Pi, the Camera case, or both.)

  One of my other projects is what I've named the 'ScamStopper', it's basically a smart call blocker.  It's my solution to stopping the Jamaican Lottery Scammers from getting through to my 93yo Grandmother.  It answers any 'unknown' caller with a message (even a custom message for the Jamaican scammers) and doesn't even ring her phone.  Only "Known" phone numbers are passed through, sans the first ring.  (And yes, we've changed her number a couple of times, but she replies to these 'surveys' and lottery 'entries' all too often, so they end up getting her new number.)  Anyways, It's quite a hack in it's current incarnation, but it works well.  It cost me about $125 just in components to build this working proof-of-concept.  I am working on refining it to cut the cost down and hopefully produce a product I can bring to market.  (IE: I'm currently using a $20 USB Modem to get the CallerID, a $40 Call Blocker device to suppress the first ring on her phone, and a $10 USB sound card [as the built-in audio was causing kernel panics, plus I wanted to be able to record on the Pi too, but haven't worked that out yet.])   

  It might also be cool to cover the Banana Pi, which is a more expensive, but more powerful version of a Pi (dual core processor, 1GB ram, SATA, etc)  I have one, but really haven't done anything with it yet, unless you count installing the "Bananaized" version of Raspibian and tinkering a little bit.  It's much faster than a Raspberry Pi, thanks to the dual cores and 1GB ram... I haven't decided what I'm going to use it for yet.

  Anyways, sorry about the 'book', and I hope you find my suggestion(s) helpful.  I hope to be a more frequent attendee now that I actually live in Worcester again...  

Jeff