During a recent project, while waiting for our Development Database to be provisioned on the clients corporate SQL Server Environment (these things can sometimes take weeks or months to be setup), we began our initial development against a local instance on SQL Server Express, just as an interim measure until the Development database was live. 

This was going just fine, until we found that we needed to do some profiling to understand a problem we were having with the performance of our ORM generated Data Access Layer.  The full version of SQL Server Management Studio includes a profiler, that we could use to help with this kind of problem, however the Express version does not, so I was really pleased to find that there is a freely available Profiler for SQL Server Express imaginatively titled ‘SQL Server Express Profiler’, and it worked great for us. 

http://sites.google.com/site/sqlprofiler/