Us europeans have a hard time. When we twitter amongst ourselves, between and during our lunches, our hard-working English speaking friends find it hard to understand what we're talking about. So I looked at 4 ways of changing how we twitter to bridge that gap.
1. Switching to English
Most of us speak English pretty well, and switching to twittering in English might be the easiest way. Some of our European friends may not like that though, and I've experienced severe peer pressure when switching to English for the briefest of moments during SXSW.
2. Adding a language notifier in tweets
I've built language detection into my diy twitter client at http://twitstat.com/m/. It works with the Google AJAX Language API, and it actually does a pretty good job at detecting language. So you'll get tweets that say '[nl] was even aan het lunchen' or '[en] that was a great lunch'.
Some of my followers didn't appreciate the ugly brackets though, and as long as there is no standard way to filter on these tags, it's not very useful. An American reader will still be confronted with the [nl] tags. Unless of course he uses http://twitstat.com/m/, in which case he can hide all tweets that contain [nl] or [fr]. Or even the word lunch, to get rid of most European tweets altogether. ;-)
3. Tweeting English in a separate account
Another option is to use one account for your native language, and one english twitter account for your foreign relations. This turns out to be very unpractical and will lead to many mistakes. I've added the option to automatically post all my English tweets to my foreign account, but you'll get funny stuff happening like replying in English to a tweet to your native account, which will then have the wrong sender in the @replies of the receiver. Confusion.
4. Automatic translation to two accounts
The final option I tried was to see if automatic translation via the Google Translation API could be viable. A dutch tweet entered in my favourite twitter client was automatically translated to english, and posted to my english account. Unfortunately, this has several unwanted effects. A reply will be translated as well, so the recipient will get 2 replies: One in dutch from my regular account, and one in English from my translated account. The other drawback is that the Google Translation API actually is complete rubbish and will only translate the most literal of sentence correctly. It really is quite poor. Check out my auto-translated feed if you don't believe it.
The only good option I see is to have the twitter client do the language detection, and then either putting the [en] tags in the tweets, or in another field that can be accessed via the API. If all twitter clients would be adapted to this, anyone could choose to filter out the languages that he doesn't want to see. This only works if all Twitter clients will add this language tag, and offer language filtering.