In Documents and Settings[USER]Application DataSaintXiLightOfAltair open the settings.ini in notepad.
After each HOTKEY_[#] there is a 1 or 2 digit number which corresponds to the buildings. Here is the list:
00 Colony HQ
01 Atmospheric Generator
02 Atmospheric Converter
03 Colonial Quarters
04 Colonial Quarters 2
05 Colonial Quarters 3
06 Hydroponics
07 Aeroponics
08 Farm
09 Solar Array
10 Nuclear Reactor
11 Research Facility
12 Goods Factory
13 *Corporate Hub 2
14 *Corporate Hub 3
15 FuelSynth
16 Drilling Rig
17 *Refinary
18 Landing Area
19 Spaceport
20 Shipyard
21 Mine
22 Orbital Receiver
23 Industrial Center
24 *Radar Facility
25 *Defence Turret
26 Shield Generator
27 Power Station
28 Hyperspace Gate Generator
29 Government Building
(Note, the ones with * do not have associated help text and do not appear to have a function yet)