I have recently started using performance insoles after having feet pain and other little things. They may not make a good pair of shoes better but they do save your feet, knees and body. Compared to very expensive custom orthopedic insoles which can be a couple hundred dollars, they do the job pretty well for around $30. I have a pair that float between my running shoes as they provide arch support, cushioning, aid form and alignment. One caveat, some of the ones with strong plastic arch and heel support can be a little thick and take a little adjusting to.
Montrail Enduro Insole
Montrail makes Montrail Enduro insoles. Montrail is originally known for their great hiking shoes and boots, these insoles compliment trail running shoes. Now they make trail runners and the Enduro insoles. The insoles are thermal bake, which means you throw them in the oven to warm them up then immediately wear them around in your shoes for so they form to your feet. At $30-$36 they are a great value and a great alternative to the more expensive custom made orthopedic insoles. These insoles sit pretty low and seem to be the best ones out there according to most people who use the Montrail Enduro Sole.
Sofsole makes a line of insoles but my favorite are the custom bake Adapt which you pop in the oven at 225 degrees and mold them to your feet. They are well cushioned and mold well. The well known custom bake Arch Molds are similar design and make a wide variety of custom bake insoles. On a side note, I've gotten a blister on my right arch due to some rubbing against the high arches on these and re-baked them hoping to fix the problem. I will be putting an Engo blister patch on them as well.
Custom bake insoles are easy to use, just take out you old insoles and insert the new insoles. They take a couple miles to break in but provide a nice level of cushioning and support that the original in soles never can. These insoles are around $30 US.