The STAI is definitely on the top of my list right now. Unfortunately it is a copyrighted instrument that needs to be purchased before administering. I am looking for freely available measures.
Those that I contribute are free to access -and even some correction by computer- at least in Spanish and through "Google" -and they are easily correctable, although their Normative Groups are for Spanish populations, as happens in ALL those that are adapted to a specific Country:
-Beck's Anxiety Inventory (BAI).
-Hamilton's idem.
-The well-known STAI.
-16 FP, in all its versions, the "2nd Order Factor" on Anxiety.
-The "EPI" of Eysenck and ditto for young people
-The Anxiety Sub Scales of the MMPI, in all its versions.