Plan a concert. Approach local musicians about donating their time. You would be surprised how many people are excited to help out a good cause.
A club night out is another way to reach people who may not traditionally be engaged by the breast cancer cause. Having your event at a local club with a fun dj is easy peasy. Clubs are made to host lots of people and they can help you with promotion. Make sure you work out all the details in advance!
A local house tour. Lots of people like to visit the interesting homes in their city. This could be an afternoon event where you go on a tour from home to home. Maybe a local interior designer or architect could be the tour guide.
Have a bake sale! Create your own homemade goodies and invite employees at your workplace to make a donation in return for your mid-morning snack.
Host your own garage sale. Take advantage of street sales in your neighbourhood to attract a good crowd. You can even collect items from friends and family to sell. Make sure to advertise that proceeds from all sales will go to Rethink Breast Cancer to motivate people to buy, buy, buy!