Yes I love Crowdbooster and use it a lot. The url shortener with bit/ly is really good but would be greater if I can read the statistics of it in the cockpit of Crowdbooster. Also Foursquare is getting popular in Holland but it gets boring soon you don't want to log in into your home everyday or your local supermarket. It might be better if you schedule your logins for foursquare and you could share this with your friends on twitter or facebook. Then you can meet your friends at places your are planning to visit. Also automatic logins into your home could be interesting so you don't have to fix this everyday.
Hope this can help you with some new ideas.
PS: I own www.followmedia.nl and want to suggest Crowdbooster in my workshops, presentations and more. Is there a possibility that I can use a logo like Crowdbooster certified partner of preffered Crowdbooster partner? That would be really nice!