MP2SL is an instant messaging and two-way chat bridge between Metaplace and Second Life. It is a robust tool for communications and remote object manipulation.

With interoperable chat, you have policy first, then use, then code, then standard. These initial forays into cross-world communication may be looked back on as milestones. (…) Miki Gymnast, best I can tell, has taken the technology component much further. I’m more intrigued by the experience of bridging worlds and the sense of shared community that it can provide. 
Dusan Writer/Doug Thompson, CEO of Remedy Communications

What Miki Gymnast eventually made is a major milestone in interoperability between virtual worlds: a communication channel between Metaplace and Second Life.
Hamlet Au/Wagner James Au, New World Notes and author of “The Making of Second Life”

But then along came Miki, who did something somewhat more complex — inserting a LAMP stack between Metaplace and Second Life, which now allows for remote control of objects in SL.
Raph Koster, Founder and President of Areae Inc/Metaplace

MP2SL is available for free, offers one-click install and is optimised for high data throughput.

Features

Once installed in your Metaplace World, you and your visitors can:

• Send realtime text messages from MP to any SL user.
• You and your friends can enjoy realtime private chat between both worlds.
• From MP you can send objects to any SL user in realtime.
• From MP you can see who is online in SL and vice versa.
• From MP you can manipulate any scriptable object belonging to you in SL.
• SL users can send messages to any user on Metaplace- 
  worlds equipped with the MP2SL system.

MP2SL has many additional features like message buffering (messages are stored if you or your chat partner is not online), MP avatar localistation (you can receive and send messages in any MP world, as long as a MP2SL device is installed there), and a spam protection for both sides. 

Check out MP2SL