Groom:
Helps with what he can of wedding planning
Plans the honeymoon
Picks the band/DJ
Picks men's attire
Mother:
Helps pick out wedding dress
Helps with the theme (flowers, colors, etc.)
Helps put together guest list and seating chart
Father:
Pays for the wedding or helps with the budget
Plans the toasts and heads them
Helps coordinate the wedding day
Deals with vendors
Maid/Matron of Honor:
Helps with whatever planning she is needed for
Plans the bridal shower (and may host it)
Sticks close to the bride on the wedding day to help out
Holds the groom's ring
Best Man:
Helps groom pick attire
Plans/hosts the bachelor party
Gets the groom ready and there on time
Holds the bride's ring
Bridesmaids:
Help make favors (if you are)
Help address invitations
Help plan the bachelorette party/ bridal shower
Groomsmen:
Help plan the bachelor party
Help the groom with any tasks he has for them
Can be ushers at the wedding
Decorate the getaway car
Non-attendant family/friends:
Provide support
Help with large jobs (favors, invitations, etc.)
May stand in the receiving line with everyone previously listed
Can be given simple tasks that the attendants don't have time for
No matter what tasks you decide to delegate, it is always vital for you to thank everyone who helped plan your big day. Some people do this with gifts, others just give a card or even just a hug. Also, always remember that they are there to help you and support you with any task you give them.