Here is a rule of thumb checklist of who pays for what:

The Bride
Wedding ring for the Groom
Attendants gifts
Accommodations for out-of-town attendants
Physical exam and blood tests
Wedding gift for the Groom

The Groom:
The Bride's rings
Marriage License
Groom's men gifts
Accommodations for out-of-town groom's men
Blood test
The honeymoon
Flowers for bride, going-away corsage, corsages for mothers, special ladies; boutonnieres for men in wedding party
Gloves, Ties, Accessories for men in wedding party
Fee for clergyperson or judge
Wedding gift for the bride

Groom's Family:
Clothing for wedding
Travel and lodging expenses
Rehearsal dinner
Wedding gift for the newlyweds

The Bride's Family:
Reception costs
Bride's wedding attire/trousseau
Invitations, announcements, thank you's, place cards, seating assignment chart, napkins and mailing costs
Photographs
Video Tape
Ceremony costs
Bridesmaids, flower girl, ring bearer flowers and accessories
Transportation for bridal party on the wedding day from ceremony to reception
All gratuities for all services: parking, security
Bridesmaid luncheon

The Attendants:
Their wedding clothes
Any travel expenses
Wedding gift for newlyweds