If you're doing some special ContentEditable work and you want to insert text into your document, you might try using the DOM. The obvious method for this is textNode.insertData(offset, str). However, when the cursor is at the insert point (such as when you're typing), insertData() won't move the cursor forward.
Solution: insertData() pushes the cursor forward if it happens anywhere before the offset. Thus we insert text and a dummy character one character before the cursor, then delete the dummy character. If the cursor is at the beginning of the text node, we simply add a new text node before it.
Rationale: The alternative to fudging the DOM is to manually reapply the position of the cursor yourself. This is reasonable in some circumstances, but requires much more logic (especially cross-browser). It can also conflict with selecting text to reset the user's selection; if it happens in the middle of a drag-and-select event, the operation may be cancelled.