Planning to advertise/publicise your site? Wish you could do it without letting a penny drop out of your pocket? There are some sites that have recently come up which allow you to do so, only difference that you use the credits instead of money to advertise your site. Credits can be earned by various ways depending on these sites. You earn credits based on number of times their widgets are loaded on your site or number of clicks, etc. Here are some sites and their descriptions :

Blogrush

First you need to create an account and submit your site for review. They have some guidelines while reviewing the blogs like some minimum no. of posts, good quality post, a quality blog, etc. so its better to read their terms and conditions before submitting your blog else you may not get a chance again after submitting 2 times. After submitting your blog you will be given a piece of code to be pasted on your site. Once you have your site accepted you will see their widget running where you had prviously pasted that code. The credits increase each time that widget is loaded or some visitors click on ads in it. These credits that you earn will be inturn used to advertise your posts on other blogs that have such widgets running !

Entrecard

Entrecard is similar service to Blog-rush that provides a small widget to be placed on to your blog. The only difference here is the way in which credits are accumulated. Credits can be accumulated by something called as "drop" in which you click on the drop logo below the widget on others site or others comming to your site drop on yours. You earn credits both way i.e. either you drop on others or others drop on yours. Other way you earn credits is by allowing ads to appearing on your widget. Its end to end advertising i.e. other people will send you request for advertising their site on your widget in return you get the credits equal to the "price to advertise on your site". You cant set your own price. Your price depends on the no of people that have droped on you. You can get full info on their site. Now you can use these credits to advertise your blog (same way as others do by sending requests to you). You can select the appropriate site based on its price to advertise. You can create your own 125x125 ad banner!. Once request approved u will see your ad displaying on their widget.

Adsflip
This is a new service which works in a similar way. When you signup you get 1000 free credits to advertise. Their widget look similar to google ad which you need to place on your site. You can create your own banner and use your credits to advertise your site. Your ad will then appear on these widgets on other sites and your credits will be consumed accordingly.