Sharing the market
The Lake Geneva Marathon is yet another event waiving entry fees for participants of the shortened 2007 LaSalle Bank Chicago Marathon. The Lake Geneva race, in Lake Geneva WI, also features a 22-mile European cross-country marathon, a half-marathon, 10k, and 5k, and routinely markets to runners in the Chicago area.
You don't have to capitalize on the misfortunes of other races, though, to lure their participants to your event. If you think it would be helfpul, offer discounts to registrants of any event you think would be attracted to yours.
You can post the offer on line, in printed entry forms, or even in the promotional materials of the race to which you are marketing. Just be sure that applicants show proof of registration in the earlier race.