This is a list of the most common banner sizes i have been asked forover the years, bare in mind some of these dimensions are for non-adult affiliate usage too....

115x115
728x100
468x60
120x60
468x80
468x100
500x32
95x65
720x60
720x100
150x600
150x400
60x120
100x100
125x400
125x500
300x30
88x32
240x60
320x60
480x60
480x100
500x100
200x200
225x225
250x250
193x80
500x250
75x75
150x200
120x90
120x240
160x600
120x600
300x600
180x150
300x250
336x280
240x400
728x90
400x82

Regards,

Lee