Nursing clothes: first month when I stayed home, i just bought a pj like shirt/gown from Walmart that has 2 holes for easy access. Also, Target sells nursing tank tops which is great in the summer.
Lanolin (PurLan or Lansinoh Lansinoh Breast Cream, 2-Ounce Bottle : to prevent crack/sore nipples. Also prevent nipples from sticking to breast pads. For sore/cracked nipples, my friend swore by the breast shells by Medela Medela Soft Shells for Sore Nipples. I never needed them because PurLan worked so well.
Washable Breast Pads Philips Avent Washable Nursing Pads 6 Count to prevent leaks. The avent and Medela set comes with a laundry bag. I like the avent b/c they don't distort with wash and Medela does. The washable ones are great if you pump exclusively. If you like breastfeed, you need heavy duty disposable pads, get Lansinoh or Medela b/c they have the absorbant gels.
Nursing Stool - Natural Oak by Medela Medela Nursing Stool or you can buy a stool at Target or at Walmart for around $10. I also use it as a step stool.
Breastmilk Pumping I had to go back to work in 1mo so I started pumping the day I came home (also to supplement). It is hard work. First few weeks, I pumped every 3-4h after I fed him (even at 1-2x/night) to establish supply. I had low supply so I took herbal supplement Fenugreek (GNC or Vitamineshoppe) which help a lot. I also continue to take multivitamins, Calcium, folic acid, fish oil and iron. Then after I returned to work, I pumped 4x/day or whenever I could. after 6-8mo, I tapered to 3x/day then 2x/day. I bought all the accessories possible to make my life easier.
Pump In Style Advanced Breastpump Medela Pump in Style Advanced Breast Pump. This is the BEST. I've used various hospital grade Medela pumps and I can attest that PIS advanced is just as good. I tried all of them, shoulder bag, backpack and Limited edition. The backpack storage area is small. The advanced system comes with a separate cooler and removable pump. Get extra pump parts. Save those kits from the hospital (the manual or kit for the Lactina) b/c they will fit the PIS Advanced. I love my limited edition bag; it doesn't even look like a pump and I can just carry the pump to and from work since I have a set of pump parts at home and at work.
Vehicle Adapter Medela Vehicle Lighter Adapter for the pump in style in case you want to pump in the car. It works really well (& well concealed!)
Hands Free Kit: this can be bought online or on ebay. You have to use the medela nursing bra. You simply need this if you're double pumping and want your hands free to do other things. I don't use the plastic attchment b/c if the bottles get heavy, they won't seal tightly. All you need is part 3007073 from Medela. Take the rubber bands and put them around the shield part where the tubing goes in.
Nursing Bra: Amazon only carries the Medela comfort line Medela Comfort Line White Nursing Bra - M which can't be used with handsfree kit. I have the seamless bras, very soft and comfortable. It has special tabs/latches to accomodate the hands free kit. Target sells a nice line of nursing bras called In Due Time tho not as soft as the seamless, but more affordable and is just like the Medela Classics. All you have to do is sew two more tabs so you can use the hands free kit.
Quick Clean Anti-Bacterial Wipes for wiping down the plastic parts in between pumping so you don't have to wash them each time. Great in theory but I still wash them.