Many hotels, hostels, motels and apartments of various quality (from no star to 5 stars) are available.
Obviously the majority of those are to be found in big cities and near popular tourist destinations, and that eastern part of Poland is less developed (and so has lower average density of hotels and such), and star rating and prices are a reasonable guide to their quality. An increasing number of those places can be found on the Internet.
Some camping sites are also available, but in the South they are opened only during summer months. In September they are already closed.
Another option for budget stays are private homes whose owners rent rooms to travellers. It is similar to Bed and Breakfast but often without the meals. Prices are usually lower than at youth hostels. In major tourist destinations like Kraków and Zakopane you will see people on the streets with signs with the words “pokoje” (rooms).