La Leche League offers breastfeeding moms groups and individual phone/e-mail help.  I highly recommend attending meetings regularly before and after your baby is born.  This is a great way to prevent problems before they begin and resolve issues before they become serious.
 

About 50% of mothers in Missouri qualify for WIC services.  One of those services is the Peer Counselor Program which provides breastfeeding information and support to mothers who qualify for WIC by trained Peer Counselors who are also WIC recipients.  Some mothers will also qualify for breast pumps.

Cotton Babies is a local retail store with locations in South County and West County.  Although their primary focus is cloth diapering, they also sell and rent breast pumps and other breastfeeding supplies.
 

La Leche League's website provides excellent general breastfeeding information.  It also offers mothers' personal stories by category - these can be a great source of support and encouragement to read about others who have been through what you are now going through.
 

Although a wide variety of breastfeeding topics are covered, they are presented in great detail - really geared more toward the breastfeeding professional but some mothers may find the detailed, research-based information helpful as well.
 

General breastfeeding information and also helpful videos teaching latch and the use of specialized breastfeeding tools.
 

General breastfeeding information in a supportive voice.

A great resource for breastfeeding mothers returning to work outside the home.
 

The Colorado Breastfeeding Coalition has put together 3 excellent videos on working and breastfeeding.

Information for mothers who are having difficulty producing enough milk.  Even better than the website is the book "The Breastfeeding Mothers Guide to Making More Milk" by the website's authors.
 

This is a special circumstance in which mother's milk production is impacted by previous breast or nipple surgery.
 

This is your go-to breastfeeding website for adoptive and intended mothers who want to breastfeed.  It contains general information about breastfeeding without birthing as well as a comprehensive resource library.  (This is my other site, especially devoted to breastfeeding without birthing mamas!)
  

This site contains the Newman-Goldfarb protocols for inducing lactation.  Adoptive, intended, and relactating mothers may find the information helpful.  However, it is very specific and induced lactation can be achieved by various approaches in addition to this one - ask me for help in finding an approach that works for your individual situation.
 

Creating a Family is a nonprofit organization offering support and information for infertility and adoption.  Their page on breastfeeding and adoption & surrogacy contains a wealth of wonderful breastfeeding information for adoptive and intended mothers.