All SAP Transaction Codes with Report and Description
Here you can see all SAP transaction codes and the called reports including a short header description.
Sometimes you are looking for transactions "around your currently known transactions". Here you have the (nearly) complete list of the SAP transactions (about 16000+) sorted by transaction code. So, you can navigate to your transaction and have a look what interesting you may find "next to" this. Just give it a chance :-)))
The full list of transaction codes is maintained in the tables TSTC and TSTCT. So, you can have a look via SE16 in your own SAP system as well.
All transactions sorted by transaction code: