Practice Your English With a Native Speaker Without Leaving Your Room

Voice chat is great for improving your speaking skills in a foreign language. These days, you don't even need to download software to do that. For example, there's Shared Talk which is a web-based flash application from the same company that created the award-winning, language-learning software Rosetta Stone. This app allows you to have a voice one-on-one conversation with a student learning your native language, in exchange for the language you are learning (in this case English--but it can be any number of different languages).
If you'd rather use a IM software, you can use Skype - probably the most popular one these days for PC to PC's calls - or yahoo or msn messengers which work really well too.
Bear in mind that in order for you to have a successful conversation, a headset is highly recommended. If you don't have one, you can always resort to regular headphones and a microphone. This greatly improves the sound quality as you won't get the echo or delay effect that is common when using loudspeakers and a microphone. Another important thing is having a broadband Internet service although that is not indispensable. In my experience, as long as one of the parties has a broadband Internet connection, you would be able to carry out a conversation successfully.