I have seen a few posts stating to put flyers in mailboxes.  Please do not do this.  This is illegal.  I used to work for a staffing agency, and this is how we found most of our employees.  The post office eventually got in touch with us and told us that this was illegal, and you MUST have postage in order for something to be placed in the mailbox, and even then, it must be placed by a postal employee.  They told us that if it happened again, they would make us pay for everyone that they found, plus pay huge fines (not sure exactly how big is "huge").

The way around this, and we approved it with the post office (which you need to do as well), is to put the flyer on the outside of the mailbox.  Roll the flyer lengthways without creasing, and place it between the mailbox and the flag.  If you do it correctly, it should stay there, even in fairly high winds. 

Make sure that you do this AFTER the mailman passes,as they generally tend to take the flyers down if ou do not have a relationship the that individual mailman (which you will, if you are out there enough).