36.6 is a new offer from Plus that offers "free" minutes in exchange for listening to commercials for a few minutes. As it has the same stingy account validity per topup, this can only be regarded as another gimmick, just like the "free minutes" you get from Carrefour Mova, which are limited to 30 a month and don't extend account validity. Starter costs PLN 9.
http://www.36-6.pl
Telepin Mobi is on the Orange network and has Orange's even worse validity policy: Topups are not cumulative, and validity is extended by max. 90 days, and if you forget to top up within 5 days of that, all your credit is stolen. Starter costs 10 PLN; it might be better to buy these and then throw them away when done. Telepin also has some other annoyances, such as the fact that voicemail messages are deleted after only 2 days. However, the main attraction of Telepin is the "low" international rates -- to most of the EU, USA, etc, it costs 50 grosz, or 39 grosz if you use the dialthrough number *169 4444. Not great, but better than what others are offering. Perhaps one of the others, or another MVNO, will try to compete with this but have a better deal?
http://telepin.pl/mobi/