Sure... Ok here is the list:

ctmod - this provides the extra ability bars at the bottom, the buff bars at the top right, and some other various functionality
xperl - the unit frames (party frame, my frame, etc)
recount - the dps meter in the lower right
multiboxer v2 - this is the grey rectangle but if you want something like this, get Jamba instead - multiboxer v2 hasn't been maintained in like a year - its a amazing it even runs
The scrolling text is just the built in WoW scrolling text

Basically I chose ctmod, x-perl, and recount because I've been using them for years and just like them/am used to them. Multiboxer v2 I am using because when I first started multiboxing 10 months ago or whenever it was, it was the only addon available to help with things that I needed for multiboxing (now jamba does everything mbv2 does and more).

I also use other non-combat related mods like auctioneer, etc