WordPress MU

Is there a plugin which allows me to redirect the blog homepage, yet allow search engines to index the rest of the blog?

you don't need a plugin, enter this line into your .htaccess file:

redirect 301 /old/old.htm http://www.you.com/new.htm

then of course change it accordingly.

I am not referring to my main MU installation homepage.

I want to redirect the homepage of a domain mapped blog which is part of my MU blogs.

How can I get the rest of the blog index by SE if the homepage is redirect by htaccess?

give us soem more info:

- what plugin do you use to redirect/map the domain to one of your blogs?

Depending on that answer we will ask you several more questions...

I am using Donncha domain mapping plugin.

ok, lets go through this from the start:

1. you installed the plugin correctly?
2. as stated in the readme, the default Apache virtual host points at your WordPress MU site so it will handle unknown domains correctly, right?
3. the user has to point his domain to your IP.

I guess the problem is 3. - that's nothing you can do, the user who wants his domain mapped to his blog in your wpmu installation, must do so himself, you can't influence clients domains.