Here is my rating of the best Media for Advertising:
Word of Mouth 10 points
Direct Mail 9
Magazines 8
Internet 8
E-Mail 8
Phone 8
Outdoor 7
PR 7
Newspapers 6
TV/Radio 3

Points were given out based on three criteria:
1-3 points for cost
0-4 points for effectiveness
0-3 points for measurability
The highest possible score is 10

Here's a break down:
Word of mouth -
Costs Nothing 3 points
Very Effective 4 points
Easy to Measure 3 points
Total: 10 points

Direct Mail -
Low Cost 3 points
Effective 3 points
Easy to Measure 3 points
Total: 9 points

Magazines -
Low cost 3 points
Effective 3 points
Measurable 2 points
Total: 8 points

Internet -
Low Cost 3 points
Low Effect 2 points
Easy to Measure 3 points
Total: 8 points

E-Mail -
Low Cost 3 points
Effective 3 points
Measurable 2 points
Total: 8 points

Phone -
Mid Cost 2 points
Effective 3 points
Easy to Measure 3 points
Total: 8 points

Outdoor -
Low Cost 3 points
Low Effect 2 points
Measurable 2 points
Total: 7 points

PR -
Low Cost 3 points
Very Effective 4 points
Not Measurable 0 points
Total: 7 points

Newspapers -
Low Cost 3 points
Low Effect 2 points
Hard to Measure 1 point

TV/Radio -
High Cost 1 point
Very Low Effect 1 point
Hard to Measure 1 point

This is all subjective of course, yet I belive it represents an accurate picture of the most effective ways to advertise. Consider this, most people have DVRs and Word of Mouth includes Viral Marketing...