Since I do not use a pest control company or use toxic chemicals around my house I have been looking for alternatives, besides vinegar. Vinegar does work for killing weeds, but what about insects, like aphids or snails. Here's some of my tricks and other resources:
Beer (any cheap beer works) in a clay or ceramic dish. Make sure that dirt is around it, otherwise snails/slugs may not crawl into as easily. I also pick any snails I find on plants and kill them., especially after watering or rain at night.
Neem oil works great, it does requires several applications if you have a bad infestation. Most directions recommend spraying infected plants in the early morning or evening hours. There are some plants that you should not use neem oil on, just read the directions.
I find that spider infestations depend on what you live in the US. Usually I don't have problems with spiders, there are only a few that do live in this area, the Black Widow, being the poisonous/dangerous one. At the moment I don't have to spray anything, I just try to knock down webs around the house and yard with an outdoor duster. You should be able to find one at most home improvement stores and they are inexpensive.
Recently I found a new product, EcoSmart (click here), that appears to be useful if you want to protect your house from insects. Currently I am trying the Garden Insect Killer product for white flies, aphids and other insects in my garden. If you are looking for alternatives this may prove to be a useful product. I might have to try the wasp product too.
And finally I found a great post at Green Living, which has many other resources too. Click here to read the article.