We've already discussed Number 5 Plastics, or polypropylene (PP)... to an extent. Recall if you will the initiatives taken by companies such as Aveda and Brita in finding uses for plastic bottle caps and water filters, respectively, to divert this previously little-recycled plastic from the landfills. Thankfully, more recyclers are accepting polypropylene, including Chicago's curbside program.
The appeal of polypropylene is that this particular polymer chain has a very high melting point, which is ideal for hot liquid containers. It is also used for yogurt containers, medicine, syrup and ketchup bottles, and straws. Once recycled, it becomes fodder for battery cables and casings, brooms and brushes, ice scrapers, landscape borders, bins, and pallets and trays.
Remember, plastics aren't so much recycled as they are downcycled-- they will never be as strong or as effective as they were at the start of their lifecycle. And although recycling is now possible, the best solution for recycling plastics remains to reduce the amount of plastic products used in the first place.