Paddles & Spankers
Spanking is one of the most popular bits of kink that most people engage in. I challenge you to find any sexually-active person who has not slapped their partner's ass or had their ass slapped by a partner during sex. When your bare hand just isn't enough (or you've used it so much your hand itself is sore), you need something to help. While quality leather paddles like the one in the link above can run around $30, there's a much cheaper way to get your spanking kicks...
When Kate and I first decided to try out some serious spanking, I picked up a pie server for under a buck at Walmart. While I plan on buying a nice leather one in the future (maybe one that leaves the word "slut" behind on her behind), for our initial experiments, the pie server worked quite well. It also has a nice serrated edge for an additional tactile sensation. Bonus! You can also try thin dowel rods, belts, and riding crops from actual farm supply stores (they seem to only be expensive at sex stores).
This is one of the first major BDSM purchases Kate and I ever made, and it was one of the best investments we've ever made in our sex life. The straps run under the mattress, the cuffs are velcro and have easy fasteners. We've used this setup and the cuffs for countless sessions of great, sexy fun.
But when we first started out, we went to Walmart (your source for on-the-cheap sex equipment, apparently) and got some soft blue rope from the outdoor/camping/boating section. We also bought a giant value box of condoms and some whipped cream. Then we ran into some of our friends from school on the way to the checkout. Everyone pretended not to know what Kate and I clearly had planned for that night (what a night, though!).
Blindfolds, Hoods, & Masks
This category of toys is perhaps the easiest to replicate for experimentation. The simple blindfold is meant to cut off visual stimulation in order to accentuate the other senses. Masks and hoods range in purpose from cutting off hearing and smell as well, to dehumanizing a submissive for purposes of the scene. The cheap alternative? For the blindfold, there's always a simple scarf, bandanna, or sleep mask. For the masks and hoods, try a pillowcase or ski mask.
This is another easy one. Once you've experimented with nipple torture with the simple option I'll give you, you can move up to more elaborate and intense versions. Start with clothespins. Actually, start with your fingers. Make sure the partner who will be on the receiving end of the nipple torture likes that pain/pleasure mix. Then move up to clothespins. (I'm kind of curious to see just how many clothespins I can clamp onto Kate's breasts before she tells me to stop....) Once you've done that for a while, if you want something more intense, look into the higher grade toys you can find in sex shops or online.
A Word on Dildos & Insertables
There is one kind of toy for which there really is no substitute. Dildos are designed for insertion and made of materials that are safe for that kind of activity. I really do not recommend attempting to cut corners on this. This is one kind of sex toy where I definitely suggest that you invest in the real deal right off the bat.
If any of you have your own DIY sex toys, let us know in the comments section. What's your favorite sex toy? What kind of creative bedroom uses have you found for everyday objects?