Similar meaning, but slightly more formal:
* Though
* Although
* Even though
* Despite
* In spite of
* Nevertheless
* However
* Yet
More informal alternatives:
* But
* Still
* Yet (can be used informally in place of "although")
* While (can sometimes be used informally in place of "although")
Depending on the context, you might also consider:
* But for
* Except for
* With the exception of
The best word to use will depend on the specific context and the desired tone of your writing.