Other means of transport in Poland

Air plane

You can of course travel between the biggest cities by plane as well. You need to remember though, that it will not be the cheapest solution.
Although the low cost airlines operate in Poland, they do not provide domestic flights, so the only carrier in such case is the national one, PLL LOT.
Any air travel between cities in Poland should take no more than one hour.

Bicycle

Riding a bike is always good fun and there are plenty beautiful places in Poland where you can go by bike. National Parks, city parks, seaside, lakeside, mountains, woods and forests are fantastic places for such activity.
Unfortunately, when it comes to cities and bike rentals only a few of them offer such possibility. Poland lacks in bike lanes, so if you decide to move around the city by one, you need to be ready to participate in regular city traffic.
There are some designated bike lanes and bike adjusted areas but not to many.
This situation is likely to change soon, but for the time being you can not expect a bike to be a convenient mean of transportation around the city.
When it comes to other areas, it is of course recommended to go on a bike trip, where you can experience Polish landscape's charm and sometimes unspoiled nature, especially in the South and South – East part of the country, like Bieszczady mountains.

Ferries

Ferries should be rather considered as tourist attractions than means of transport, but if you are somewhere in the countryside, they may be the only way to get to the other side of the river.
If it happens that you have a chance to use one, definitely do so.
Ferries as tourist attractions are present at Baltic Sea and in Mazury region, the biggest lake district in Poland, one of the most attractive tourist destination for both Polish and foreign visitors.
It is also a fantastic region for bike tours.