Weebly lets you back-date posts, and the it supports rich copy-paste, so I've re-posted some of my more recent blog items from the old site... 
EDIT: to answer the comment below, when you create/edit posts, there's a little calendar indicator next to the date (see below). Click that and choose a date from the pop up date-picker.

So now that posterous has closed up shop, having a look at weebly. Seems to have a lot more to offer... but no way to bulk upload my old content... ho hum...