With gas prices rising, it seems that even people that weren't buying in bulk before are considering it and will now buy bulk products. If you're going to buy bulk and haven't before, you might want to start out small unless you are working on getting a years supply of food like LDS families do. (For more information on that, check out the LDS Food Storage Calculator).
If you are looking for organic or locally sourced ingredients, you can usually find a co-op type farm that delivers on a route on a specific delivery time line. For the North West, check out Azure Standard. You will have to order a minimum amount if you are not a part of a preexisting drop, so call to see if there is one in your area. If you're not in the Northwest, a Google search should be able to find you a co-op that delivers in your area, or ask around in your local organic food store.
Buying bulk food online is going to cost you a pretty penny in shipping, and if not in shipping, then in packaging. A lot of it will be packaged as "emergency food". If you want it to be as long lasting as the "emergency food" that is selling on the websites there are a few things you can do, but you will need to package it well. Most of the "emergency food" is in 5 gallon buckets or super pails (which I think are 6 gallon buckets) with the actual food in a Mylar bag and an oxygen absorber. So all you need to do to keep your bulk food you buy from the store as fresh is put it is buckets with Mylar bags with and oxygen absorber. NEVER put an oxygen absorber in with sugar unless you want it to be a brick. When you seal the bags, you need to make sure that as much oxygen is out as possible. Google around for more information, I am not an expert on this.
If you are going to use your food in a reasonable amount of time you can just put it in buckets for storage. You can either buy buckets, which are a little pricey (you need FOOD GRADE plastic, DO NOT use anything that held anything toxic such as paint, primer, paint thinner, chemicals, etc) or you can go to your local bakery and ask them if they have any extra buckets. They will usually have extra frosting buckets laying around. It helps to call ahead and have them save them for you. Sometimes they will charge you $1-2 for each bucket, but at the store buckets go for about $5-7 so you're still saving money. If you don't want to pay, try calling a different bakery. If the lids they provide you with don't work, you can buy lids. Lids are cheaper than buckets.
You WILL have to clean out the buckets. It's what you get for getting cheap/free buckets. Even if they look clean, you want to clean them out well, with soap. Hopefully you have a utility sink because, well, they're buckets. Otherwise try to set up a station outside near your hose and use a non-toxic soap that won't kill outside plants.
What to Buy
Buy what you eat. Packages have been shrinking. I have noticed it. I don't know if you have noticed it, but cereal boxes are getting smaller, cans are getting smaller, and I am getting less for the same amount of money. There is one thing that doesn't change. A 25lb bag is a 25lb bag. A 50lb bag is a 50lb bag. 25lbs of oatmeal is nutritious, will make great cookies, breakfasts, won't shrink, and is great on the budget. A 25lb bag of rice usually cost less than a 5lb bag of rice. I paid $11 for our 25lb bag of rice. How much did you last pay for rice? Oatmeal? My 25lb bag of oatmeal was $15. You can even buy Sea Salt in bulk if you are so inclined! Granted, it will last you for a bajillion years, but for $8, I just couldn't pass it up. I got all of my bulk foods from WinCo. They also have a ton of different kinds of beans.
So buying in bulk is great. I love it, you can find a lot of different products, and it can save you a lot of money. Find what works for your family. If you buy something they're not going to eat, it's not really saving money. If you buy products you regularly use and are in regular rotation, you will be doing yourself and your wallet a huge favor.