I was actually just going to post a similar question.  Let me answer yours first...then I'll post mine.

You can change the text of read more through Admin, Languages.

Choose Language Editor.

Expand Local Resources, Desktop Modules, Announcements, App_LocalResources and choose Shared Resources.

Change the Localized Value of the More.Text.

Now....here's MY question:

Does anyone know of a way to change the Read More link text on a SINGLE Announcements module without changing it for ALL Announcement modules on the site?

Hello Mike,

Thanks for your reply.
I followed the steps and changed the Localized value of the More.Text but nothing happened. It didn't reflect to the new text, it still reads read more ... Do I need to purge the changed text somewhere, if so how do I do it? When I check Highlight Pending Translations, the More.Text field is not surrounded by a red box while others are (although shouldn't it be the other way round meaning that the pending translation should be in a red box) so I believe that it needs to be purged somewhere but where? And what about using an image. Is it the same procedure? Do I have to use the FCK editor to upload the image and use that?

You assistance is much appreciated.