Some of the answers to this question deal with older versions of Cassandra. The correct answer for this kind of problem depends on the version of
This answer dates to before the release of Cassandra version 1.2, which provided substantially different functionality for handling lists. The answer might be inappropriate if you are using Cassandra 1.2+.
As mentioned on the mailing list, my preference which has worked very well for me, is to store a single column "skills" with the value being a serialized JSON string.
Really comes down to the usage patterns you have for "skills".