Here are some interesting tweets related to ISRO's Mangalyaan being successfully inserted into Mars orbit:
From NASA, USA:
NASA @NASA, 7:47 PM - 23 Sep 2014
We congratulate @ISRO for its Mars arrival! @MarsOrbiter joins the missions studying the Red Planet. #JourneyToMars
From NASA's Mars Curiosity:
Curiosity Rover @MarsCuriosity, 8:03 PM - 23 Sep 2014
Namaste, @MarsOrbiter! Congratulations to @ISRO and India's first interplanetary mission upon achieving Mars orbit.
ISRO's Mars Orbiter response:
ISRO's Mars Orbiter @MarsOrbiter, 8:32 PM - 23 Sep 2014
Howdy @MarsCuriosity ? Keep in touch. I'll be around.
[Ravi: I thoroughly enjoyed the tweet exchange between NASA Mars Curiosity and ISRO Mars Orbiter. Really great short message exchange announcing India's entry into a select club of nations in another planet. Of course, the actual tweeters and the tweet exchange would be between two earth-located representatives associated with the above two Mars missions. But even then the tweet exchange is great to read.]