I've always thought interactive text reconstruction activities (eg http://www.cict.co.uk/software/textoys/examples/example2.htm) were really useful for spelling improvement, but they're not easy to do on paper. A good alternative is a code words exercise, in which you see some letters in the text and have to guess others to reconstruct it. Doing the puzzle really makes you think about spelling, as well as meaning and grammar - a full workout really!
And for learners who find writing difficult, this can make a great model for their own writing.
Here's one I made. This is a guided one: there are hints to help learners solve the puzzle and think about spelling. Feel free to print it out and use it. The second page is the key. If it's too difficult learners could read the full text first or the teacher could read it out.
This is the first one of these I've ever made, so feedback welcomed. Especially if there are any mistakes!!
Code Word Nouri