Invitations:
Send out 8-10 weeks in advance.
May want to send "save the date" cards 6-8 mos. in andvance.

See web sites or books below for wording. It will be different if wedding is in a house of worship than it is for some other place.

Guest List:
1/3 couple, 1/3 bride's parents, 1/3 groom's parents
Or 1/4 bride, 1/4 groom, and 1/4 each parents.

Non-married couples:
Emily Post's "Wedding Etiquette" book says couples living together must be included.
See: EmilyPost.com/weddings/planner/guest_lists.htm

Bridal Guide Magazine says:
"Those who are engaged; those who are cohabiting; and those who have had a steady significant other for so long that it would seen awkward not to include him or her. The last instance is a judgment call, but in most cases your gut will tell you what to do."
See: BridalGuide.com/default.cfm?fuseaction=request&item_id=148#GUESTDATES

Co-workers:
- If you invite anyone, you should also invite your boss.

Books:
"Wedding Etiquette", 2005, Emily Post
"New Etiquette for Today's Bride", 2004, Bidal Guide Magazine
Martha Stewart Weddings, revised quarterly
One Perfect Day, 2007, Rebecca Mead. - According to Mead, the American wedding is an exercise in cheap sentiment and pricey self-indulgence, orchestrated by an industry that cunningly plays on the romantic delusion of the betrothed.
In her NY Times review, Jodi Kantor says: "Weddings, unlike most other things we purchase, reliably deliver heart-stopping measures of joy."

Magazines:
Bridal Guide
Modern Bride at Brides.com

Links:
EleGala.com
Emily Post
Bridal Guide magazine Traditions & Etiquette
weddings.about.com
Online Wedding Planning Guide, Wedding Ideas, Links & Information at TopWeddingSites.com
OurMarriage.com/
Atlantic City Weddings - Elaine's Etiquette Guide
Bridal Shower Gift Ideas