For those with extra time and a love of trains, high altitude scenery, and cultural tourism, I recommend the Ferrocarril Central Andino Train from Lima to Huancayo.

http://www.ferrocarrilcentral.com.pe/en_cronograma.html

It runs somewhat on a somewhat irregular schedule from now through mid-November. I was able3 to buy the ticket online, but it took weeks to process the credit card, and the same would be true for any refund. There may be better options to purchase them in Lima at one of the supermarkets.

it is a full day, though spectacular scenery, and at one time the highest train service in the world. As you reach the highest elevations, there is a nurse on board who has medication and oxygen available (she actually goes through the cars and checks on people who are getting drowsy, an early sign), I went to Cusco to acclimatize for the train!

Huancayo itself is not particularly developed for tourism, although there are group tours as well as private tours available to outlying communities, probably best arranged in advance since there are only a few operators. There are some links on the FCCA website. I stayed at a guest house that I won't recommend to the typical Fodorite, but it was bookable on short notice through hostelbookers. Actually it was comfortable enough, other than tons of barking dogs and a somewhat sketchy neighborhood.

I wound up visiting the Huancayo Sunday market for an hour (mostly it is commercial goods, but a few interesting photo ops. Really the highlight was going to the Cochas communities and by sheer luck stumbling into a traditional dance performance of the Chonguinada. There is regular bus transport to this town as well as taxis, or you can possibly book a tour, but it's likely to be highly market up.

Good food in the market for breakfast, and there is a cafe in the mall (yes) that is not bad.

Photos to tempt you onto the train
http://photoperuana.wordpress.com/