Preferably stuff that I can make at home.
For aphids, you can mix a tiny bit of dish soap in water and spray it on them. For many insects, a strong spray of water from your hose will knock them off as well.
I use white vinegar and water to kill ants, and I assume it would repel them if it didn't evaporate.
Search for "companion planting" on the web and you'll find other PLANTS you can plant nearby to repel insects, like marigolds. I also plant radishes nearby other veggies because some insects like them much better and will eat them and leave the other veggies alone. You can also plant beneficial plants to encourage a pest's predator to hang out near your plants (again, search "companion planting").
ex. –
http://www.gardenguides.com/how-to/tipstechniques/vegetables/vcomp.asp