I'm a pretty heavy user of IMGRed, which caches images for me in my posts. Below is a cached version of the WriteToMyBlog logo image:
To you as the reader, you see the image and the IMGRed caching is invisible, which is how everything should work.
Here's what I'd like to see on WriteToMyBlog:
When I click the "Insert/edit image" button and get the dialog box to put in the image URL, give me a check box that automatically appends "http://imgred.com/" before the URL that I paste in.
I love WriteToMyBlog and this truly is a wishlist feature request.
Link -- IMGRed
Link -- WriteToMyBlog