Plan to pay for your wedding party's flowers (bouquets, any flowers for their hair, and boutonnieres) and their lodging, if they don't live locally. Lodging doesn't have to mean a hotel room—it can often be found with family or close friends who offer to help host guests. Also, plan for gifts from the bride to her bridesmaids and the groom to his groomsmen as thank-yous for being in the wedding party. The bride usually gives all of her bridesmaids the same gift; ditto for the groom to his groomsmen. The gifts can be anything from a small token to a serious gift, and are usually given privately in the days before the wedding, or publically at the rehearsal dinner. It's popular to give part of their wedding attire as a gift they can use again; jewelry for the ladies and ties and/or cummerbunds for the gentlemen.
Attendants pay for their wedding attire and accessories (shoes, hair pieces, ties, etc.), whether rented or purchased, and they pay for their flights or drive to the town or city where the wedding is taking place. As for gifts, the bridesmaids contribute to their present for the bride and the groomsmen do the same for their present to the groom.
Interestingly, while it's very common for bridesmaids to host or share the cost of pre-wedding parties, such as showers, bachelor or bachelorette parties, or bridesmaids' luncheons, it's not "required." This is always especially stunning to bridesmaids who thought throwing the bride a shower was part of the job description. It used to be poor form for the bride's family to throw her a shower, as it looked like a thinly veiled plea for gifts, so the party was often thrown by the bride's closest friends, in most cases her bridal party. —Anna Post, The Emily Post Institute