A nice idea to get practice using your target language is to start a diary. You can keep it private by writing in an actual diary, or you can publish it on the internet in the form of a blog. This can be useful as native speakers may read it and post back corrections or encouragements.
If you are familiar with Wordpress or another blogging website you can just sign up for a new blog and post in the target language.
Another way is to join a social network in your target language. This has the added benefit that the entire website and the majority of the users will be in the target language.
Here are some social networks in languages other than English:
Skyrock - Mainly French, also in German, Spanish, Dutch, Italian, Portuguese, Finnish, Swedish, Danish & Norwegian.
Studiverzeichnis - German
Mixi - Japanese
Cyworld - Mainly Korean, also in Chinese, Japanese, Vietnamese & German.
Friendster - Malay, Thai & Indonesian
Cloob - Persian
Mitleap - Khmer
Another alternative is Lang8, which is specifically for people learning languages. You post a diary entry and native speakers will correct it for you. In return you read other diary entries in your native language and correct them. It's a nice way to improve your writing and help other people. See here for a more indepth review.
I enjoy films and TV shows so I like to use foreign language videos as a way of practising listening skills. You may have heard of people who spend all their time watching foreign tv and come out fluent at the end of it. Although this is likely to be a much simplified version of the truth; films & TV can improve your language skills immensly.
When I am watching something in a language I am not very familiar with (beginning level), I watch it twice. The first time I watch with subtitles to try and match the subtitles with the words I am hearing. The second time I watch without subtitles, to try and see how much more I can understand when I know the gist of the story.
If I'm fairly familiar with the language (intermediate and above level) I also watch it twice, however I reverse the order. I watch the first time without subtitles to see if I can understand the storyline without having a translation. The second time I watch with subtitles to catch any words I missed the first time.
Try either one of these methods and see which one works best for you.
Novels, magazines, comics, children's books etc, are also a popular method of improving your language ability.
Choose material you're interested in. If you have a specific interest (e.g. airplanes) then read about it in your target language, not your native language.
Try reading material that is little bit beyond your current level. Not too easy that you understand everything, not too hard that you are totally lost, but still a bit challenging. Here's a rough guide to difficulty levels of reading materials, from easy to hard:
Signs, picture books, 'readers'
Teenage books, magazines, self-help books, light non-fiction books
Serious novels, non-fiction books
Some people advocate 'thrown in the deep end' approach but this will more likely leave the beginning learner totally lost. Try varying between easy and hard material if you want.
If you are looking for authentic material in your language one of the most convenient is news sites. It can also give you things to talk about with native speakers and teach you current vocab that you are unlikely to learn in textbooks. Another advantage is that news sites are very frequently updated, meaning you are never short of interesting things to read or listen to.
BBC (32 languages), Deutsche Welle (30), NHK (17), RFI (19), CRI (44), Euronews (8), VOA news (45), RFA (10), KBS World (11), SBS radio (68), TRT (30) and RNW (10) all offer up-to-date news and radio segments in a huge array of languages.
If you normally read the news in your own language why not give yourself a challenge of reading the news in your target language instead? Try taking one article at a time, looking up any words you don't understand, and go over it a few times to make sure you understand.
Of course, unless you especially like challenges, you will probably need to be at least an intermediate level, or high beginner, to get the most out of this type of material. If you find news articles too challenging right now, try coming back later in your language studies.
Podcasts are basically like radio shows, except that you can download each episode at your convenience. As they often offer a huge archive of past shows, it's an easy source of interesting listening material. Most popular languages will have a huge variety of podcasts covering different subjects, so pick ones that interest you. If you have iTunes, you can check what podcasts are the most popular in each country.
Some podcast repositories:
Podster.de - German podcast depository.
RTHK - Cantonese podcasts from the channel RTHK.
mixPod - Recommends Japanese podcasts.
Podcasting Juice - Big repository of Japanese podcasts.
Podcasters - Directory of Spanish podcasts with recommendations.
Podcast.it - Italian podcast portal.
Audiocast.it - Italian directory with more than 1000 podcasts.
Podics - Repository of Korean podcasts.