Traffic exchanges and safelists can be a great way to advertise your business, affiliate program, product, service, etc. without any cost to you. They allow you to get your message in front of targeted prospects instantly.
Traffic Exchanges
Traffic exchanges involve surfing through other people's ads in exchange for credits. When you earn credits, your ads are then shown to other surfers. You can view, or surf, as many ads as you want. The more your surf, the more your ad is shown. It's completely free to join a traffic exchange. Most also offer a paid membership for increased benefits.
There are also text ad exchanges, banner exchanges etc.
incorporated into some of the sites.
Here is a list of my recommended exchange sites:
Traffic Swarm
Click Thru Traffic Exchange
eCash Traffic
Traffic Roundup
Viral Ad Machine
List
Surfing
Free Traffic Lotto
More coming soon...

Safelists
Safelists are free membership sites you sign up to and agree to receive email advertisements from other members. In return, you're allowed to send out your own solo email ad to the entire, or limited list of members. There's usually a free and paid option available for safelists. This is a great way to test your email ad content and subject line until you fine-tune it for best results.
The great thing about safelists is that all members are 100% opt-in, so you won't ever have to worry about spamming anyone.
Here is my list of recommended safelist sites:
List Jumper
Business World List
Cash-Blaster
CashSpeeder
List Bandit
List Dot Com
Your Lucky List