To learn a language fluently, one have to read, write and listen it regularly. There are numerous websites on the net where you can read, write, listen and discuss things. Some of them are as following:
Tolafghan, Benawa and Talafghan are the most read, full Pashto websites where you can read articles, essays and books on almost every subject, and news. Tolafghan has a vast forum where you can discuss issues with the other members.
Khyberwatch, Pashto and Afghanan are the websites launched for Pashto by the Pashtoons, but their language is English. Useful information could be found on these sites. Each of them has a forum.