According to the modern standards of education essays are considered a proper means of developing students' skills.They help to improve writing skills, elaborate the style, expand the outlook and maintain creativity.
But if to dwell upon the latter aspect in particular we should bear in mind that creativity can be developed only if the topics suggested for essay writing presuppose it.For example, we cannot expect something original from the essay if the topic sounds "My summer vacation" (that is still relevant for some teachers and is given as the first hometask in September).
Probably it's difficult for me to make a fair judgement as I work with university students who have already formed a particular point of view on any issue and are eager to express it and are proud of being original but I strongly believe the essays should be applied but their titles should provoke creativity.
It will make your students be quick with handing their papers in on time and it will prevent them from using Internet essay samples.
My students normally write essays on the books we read; one of the latest was devoted to the comparison of the book and the film versions of "About the Boy" by Nick Hornby.But I do offer them essay topics in the framework of the material we study; for instance, dwelling upon daily routine with freshmen I do not ask them to write about their typical day but about a day of an inanimate object's life, it can sound like "A Day in the Life of a Spoon".You may find it sound odd but students appear to be much more responsive and creative writing about a spoon than about themselves and I achieve the goal as they use the vocabulary we studied and they learn to express their thoughts in a comprehensive way.

And what essay topics do you suggest for your students?