For open source or generic computer science topics, I think it is indeed difficult to come up with much in the way of useful new or interesting content.

Do you use any proprietary or closed source products? Many (not all) of those have poor quality, perfunctory documentation, and if you work with them a long time you'll development knowledge by means of experimentation, reverse engineering and support tickets.

Try blogging some of that, or develop it into some alternative documentation, book, or presentation. Become a well-known independent expert.