In this blog entry I've collected all confirmed Droid models that appear in the Saga. If you know any more, please let me know!

2-1B Surgical Droid - Geentech - III V VI
3PO Protocol Droid - Cybot Galactica - I II III IV V VI
8D8 Smelting Droid - Roche - VI
ASN-121 Courier Droid - Malkite Poisoners - II
ASP-7 Labor Droid - Industrial Automaton - IV
B1-Series Battle Droid - Baktoid Combat Automata / Geonosian Industries - I II III
B2-Series Battle Droid - Geonosian Industries - II III
BD-3000 Luxury Droid - LeisureMech Enterprises - III
BT-16 Perimeter Security Droid - Arakyd Industries - VI
Pistoeka Sabotage 'Buzz' Droid - Phlac-Arphocc Automata Industries / Collicoid Creation Nest - III
CLE Cleaner Droid - PublicTechnic - II
CLL-M2 Binary Loadlifter / Ordnance Lifter - Cybot Galactica - III
COO Cooker Droid - Industrial Automaton / PublicTechnic - II (C)
CZ Secretary Droid - Serv-O-Droid - IV VI
DD-13 Medical Droid - Ubrikkian Industries - III
Destroyer Droid P-Series - Collicoid Creation Nest - I
Destroyer Droid Q-Series - Geonosian Industries - III
Destroyer Droid W-Series - Geonosian Industries - II
DRK-1 Dark Eye Probe Droid - Arakyd Industries - I
DSD1 Dwarf Spider Droid - Baktoid Armor Workshop - II III
DUM Pit Droid - Cyrillia / Serv-O-Droid - I II
EG-4 Power Droid - Veril Line Systems - IV
EG-6 Power Droid - Veril Line Systems - V
EG-9 Labor Droid / Temirca Droid - Unknown - I
EV Supervisor / Interrogator Droid - MerenData - VI
FA-4 Pilot - SoroSuub - II
FA-5 Valet Droid - SoroSuub - III
Forklift Ammunition Droid - Unknown - III (!)
FX-6 Medical Assistant - Medtech Industries - III
FX-7 Medical Assistant - Medtech Industries - V VI
G2 Repair Droid - Soro Suub - Star Tours
GH-7 Medical Analysis Unit - Chiewab - III
Giant Mouse Droid - Unknown - V VI (!)
GNK Power Droid - Industrial Automaton - I II VI
HL-444 Hover Loader - Arakyd Industries - III
HMP Heavy Missile Platform - Baktoid Fleet Ordnance - III
IG-100 Bodyguard / Assassin Droid - Holowan Mechanicals - III
IG-227 Hailfire-class Droid Tank - Haor Chall Engineering - II
IG-88 Assassin Droid - Holowan Mechanicals - V
Imperial Mark IV Sentry / Patrol Droid - Imperial Department of Military Res. - IV
INS Installer Droid - PublicTechnic - II
IT-O Interrogator Droid - Imperial Department of Military Res. - IV
IW-37 Pincer Loader - Cybot Galactica - III
J9 Worker Drone - Roche - VI
JN-66 Analysis Droid (at the left) - Cybot Galactica - II (*)
KPR Security Droid - Lerrimore Droids - IV
LIN Demolitionmech - Cybot Galactica - IV
LM-432 Crab Droid - Techno Union - III
LOM Protocol Droid - Industrial Automaton - V
Marksman-H Combat Automata - Industrial Automata - II IV
M-HYD Binary Hydroponics Droid - Unknown - IV
Pria Assemblage Chroon-Tan B-Machine - Polis Massan - III
MixRMastR Bartender - Cybot Galactica - II
MSE-4 Mouse Droid - Rebaxan Columni - III
MSE-6 Mouse Droid - Rebaxan Columni - IV V VI
Information Cataloging Droid - Mustafar Panning Droid - Kalibac Industries - III
Mustafar Industrial Droid - Unknown - III (!) (Hyperspace picture)
Naboo Lawnmower Droid - Unknown - I (!)
NR-N99 Persuader-class Droid Tank - Corporate Alliance - II (*) III
Octuptarra Droid - Baktoid Armor Workship - III
OG-9 Homing Spider Droid - Commerce Guild - II III
OOM-Series Battle Droid - Baktoid Combat Automata - I II III
Otoga 222 Maintenance Droid - Veril Line Systems - I
P-100 Salvage Droid - Cyrillia & Serv-O-Droid - I III (*)
PK Labor Droid - Cybot Galactica - I II
Hologlide J57 Cam Droid - Industrial Automaton - I
Prowler 1000 Probe Droid - Arakyd Industries - III
Q7 Astromech Droid (in V-Wing) - Industrial Automaton - III
R1 Astromech Unit / Mark III Reactor Drone - Industrial Automaton - I IV
R2 Astromech Unit - Industrial Automaton - I II III IV V VI
R3 Astromech Unit - Industrial Automaton - II IV V
R4 Astromech Unit - Industrial Automaton - II III IV V
R5 Astromech Unit - Industrial Automaton - I II IV V VI
RA-7 Death Star Droid - Arakyd Industries - IV
RIC General Labor Unipod Droid - Serv-O-Droid - II
R-PK Droid - Cybot Galactia - I
Scrubber Droid - Industrial Automaton - I (!)
Senate Cam Droid - Unknown - I II (!)
SP-4 Analysis Droid (at the right) - Cybot Galactica - II (*)
SRT Autonomous (Short Range Transport) - Baktoid Combat Automata - II
'Stretch' Droid - Unknown - I (!)
Talking Magnetite Cleaner - Unknown - I (!) (picture see 'Visual Dictionary TPM')
TC Protocol Droid - Cybot Galactica - I III (**)
Tri-Droid - Techno Union - III
Tri-Fighter Droid - Phlac-Arphocc Automata Industries - III
TT-8L Sentry Droid - Serv-O-Droid - VI
Variable Geometry Self-Propelled Battle Droid 'Vulture Droid' - Haor Chall Engineering / Baktoid Armor Workshop - I III
Viper Probe Droid - Arakyd Industries - V VI
V-series Supervisor Droid - MerenData (***) - VI
WA Waitress Droid - Go-Corp / Utilitech - II
WED-10 Treadwell - Cybot Galactica - IV V VI
WED-15 Treadwell - Cybot Galactica - II IV V VI
WED-9 Treadwell 'Bantha' Droid - Cybot Galactica - IV
Welding Droid - Unknown - I (!)

Unknown Protocol (?) / Medical (?) Series - Unknown - VI (Jabba's victim)
Unknown Droids in Watto's Shop - Unknown - I (picture in Chronicles: Prequels)
Unknown Mining Droid at Mos Espa - Unknown - I

Naboo Starfighter support Droid - Unknown - I (!) (**)

(!) Droid model does not yet have a more detailed name, type or series
(*) Deleted scene
(**) Unknown if the Protocol Droid in III are TC models
(***) Uncertain, but MerenData developed the EV-Series
(C) Contradicting sources (Fact Files & New Essential Guide to Droids)

I want to thank 'Wild Whiphid' who was my partner in crime for this blog. Good job!