Hay

Pet Store
Pet stores will carry a variety of hay (i.e. Timothy, orchard grass, alfalfa, etc.). Typically, the amount that can be bought will range from about 24 oz up to 5 pounds. Although it is convenient to buy hay at a local pet store, this is often an expensive option. A 64oz bag will usually last a couple of weeks at ~$8. Additionally, most pet store brands offer lower quality hay that is very hard and stalky. The recommended popular hay brand is Oxbow, although this may be quite expensive since they carry a premium price compared to other commercial brands.

Some brands may offer fruit mixed in the hay -- DO NOT BUY THESE. Fruit is not necessary for a rabbit and contains a lot of sugar. If your rabbit does not seem to be eating his hay (which is a giant problem), cut down on other sources of his diet (i.e. vegetables, pellets, and treats). If he has no source of food but the hay in his living space, he will consume the hay. Only buy bags of hay with only hay in them and no other treats. You can feed fresh healthy treats on the side, independent of the hay and easily rationed.

Through the Local HRS Chapter
If you live in a location with an HRS chapter, check and see if they sell boxes, flakes, or bales of hay at a cheap price! Of course, buying a bale yourself will be cheaper, but if you do not have the space to store it, support your local HRS chapter! They will most likely sell fresh hay at a better rate than the small bags at pet stores. Your bunny will mostly likely love and wallow in the fresh hay.

Some examples of HRS chapters that sell hay include the following:
 * San Diego House Rabbit Society, San Diego, CA -- $12 for 10-12lbs of hay
 * House Rabbit Society Headquarters, Richmond, CA -- $5 for a flake (garbage bag full) of hay

Online in Bulk
Some bunny owners like buying their hay online in bulk. Some of these suppliers also ship much fresher hay than the average commercial brand.

The following a list of reputable online retailers in the US:
 * American Pet Diner
 * Bingaling Bunnybox Store
 * BunnyBale
 * BunnyBytes
 * BunnyLuv
 * KMS Hayloft
 * Sierra Valley Pet Hay
 * Sweet Meadow

By the Bale
The cheapest option typically is a bale of hay. One bale, typically ~70-110lbs depending on type, can feed one rabbit for a year. However, this requires space to properly store the hay as it is easily perishable when wet.

How to Store Hay
It is very important to keep hay dry and out of direct sunlight. Dampness will cause mold in the hay, and sunlight may leech out nutrients in the hay over time. The best location to store hay is in a cool indoor location out of direct sunlight.

If you must store hay outside, invest in a waterproof tarp along with some bricks to keep the hay off the ground.