I just got my 150 last week and next I plan to order the Sennheiser EW100ENG G2 wireless mic system. Just curious as to what kind of mount you all recommend to go with the 150.

Also, will I need to order additional accessories when I get my tripod (still weighing tripod/monopod options)

There's a couple of options, the wireless ships with a camera mount kit to place the unit in the HMC150's cold shoe. It looks like this:

Sennheiser Wireless G2 hot shoe set-up on Vimeo

You also have the 1/4"-20 threads to screw in additional accessories or you can use something like the bracket1

Bracket1 - Camcorder Accessory Solution on Vimeo

Velcro on the camera battery.

You can also mount one of these to the 1/4 20 thread in the handle and mount the wireless there.

bogen magic shoe (http://www.bhphotovideo.com/c/search?Ntt=bogen+magic+shoe&N=0&InitialSearch=yes)

I use the cold shoe for one unit, I also have an L shaped bracket that attches to the shoe, that I can use when mounting two of the Senn's.

I just got my 150 last week and next I plan to order the Sennheiser EW100ENG G2 wireless mic system. Just curious as to what kind of mount you all recommend to go with the 150.

Also, will I need to order additional accessories when I get my tripod (still weighing tripod/monopod options)

I mount the G2 receiver directly to the cold shoe mount on the camera.