After I've tried BloGTK, Drivel and gnome-blog-poster, I must say none of them did the job satisfying.
None of them were able to do a title, and none of them could do English spellchecking.
Drivel had a nice "edit old post" function, but gnome-blog-poster had a gnome-panel applet, so I find that it might be the best solution of the three.
However as none of them were able to post titles to posts, they weren't really useful. I guess I have to just use the web interface for now.