You may have read about a bridesmaid luncheon or tea in a wedding planning book but I don't think I know anyone who planned or attended one.
A bridesmaid luncheon or tea is a party the bride hosts in honor of her bridesmaids as a thank you for being her support system while planning her wedding. When I was planning my wedding I decided to host a tea party for my 'maids. Unfortunately things got busy between planning my sister's shower and wedding and my wedding within a few months of each other - and my grandfather passing in between - that I decided to cancel the bridesmaid tea.
But if you can swing it it's a nice way to spend non-wedding planning time with your closest friends. And if tea isn't your thing you can make it a day at the spa or another outing but make it something about your girls and not your wedding.
This party may also be a good time to hand out bridesmaid thank you gifts, especially if the gift is something they can wear or use at the wedding.