As well as a lot of natural conversation, I love mixing games into my Portuguese classes! Since you are using this online, here are two very cool places where you can find a bunch of online games to practice Portuguese (great resources for teachers also):
- Português em Badajoz - This site, created by Portuguese teachers in Badajoz (Spain) has a bunch of links to great online games/quizzes. The descriptions are all in Portuguese, so you may have to poke around a little bit for something that is just right for you. Some of the quizzes (e.g. Os contrários in Jogos de associações or these games by Instituto Camões) will be great for beginners. Other games (eg. Espaço Lusofonia) will be better for intermediate or advanced students.
- Ludo-tech - This site also has a great collection of games (all created by the writers of the site). It seems like some of the games may have been designed to teach Portuguese children (whose first language is Portuguese to begin with :-)), but most of them can also be useful for second language learners (like this vocabulary quiz).