This is the only solution I have ever used. I have been useing a web based chat system through our hippo vend, rental boxes. you can send messages from the internet, by logging into your account with hippotech, and have your IMs set to be recieved in email.... you will be able to see people talking to you in your email, and speak back through your hippotech account.
I have also used a tiny installable program, that allows your avie to rez inworld, and have another avi contol it through voice chat, but the system allows for chat as well. http://www.metabolt.net/
on my cell phone there is an app: lumiya it has FULL control over your SL life. it has visual, inventory, and the entire people section of the SL viewer. (PS i run an old andriod... 2.something, and it works fine.
I am unaware of any web based all inclusive web based chat possabilites, other than stuff I have developed.... which basically implements a web based chat room, and a special gadget in SL that has access to that same chat room.
see my device in the Galifry Mall: http://maps.secondlife.com/secondlife/Gallifrey/150/87/69