Below is a summary of all the winning codes thus far and the 'yay' messages the winners wrote in no particular order at all. Notice I'm missing some links -- If anyone finds some more, do tell.

280302
ElGamal, all variables xa=255, ya=255, k=27, m=15, p=307, g=10 using http://t.co/HBGWtGB and the answer is c1+c2=280302, (255, 255, 27) is a guess of what colour the yellow poster was in RGB
yay msg

BTFPCW
Ballerina, Taxi driver, Footballer, Poster, Child, Watchmaker
yay msg

AMEYER
Head of industrial design at Nokia
yay msg

LLORAH
Taxi driver’s name
yay msg

248338
Da Vinci’s birthdate in base 9
yay msg

C3CE97
1st 6 characters of the MD5 hash key of “Stepin”
yay msg

GNBWAT
9th letter in each of the YouTube video descriptions
yay msg

IRFNOM
Mon-Fri spelt backwards
yay msg

850630
8:50 and 6:30, both alarms set by the girl
yay msg

210611
Date on the N9 of the football player
yay msg

132545
Time set on the watchmaker’s clock
yay msg

915914
Time on the football player’s N9

041434
Taxi’s distance meter

STEPIN
The 6 hidden letters

HPMHMK
KM/H MPH backwards

DCA578
Taxi’s plate

PRND21
Taxi’s gears

7AM7PM
Road panel

436793
Toronto coordinates 43.655314,-79.365733

Unverified yay msgs:
no. 1
no. 2
no. 3