How to get the last month data and month to date data

Need help in writing the query to get the last month data as well as month to date data.

If today's date is Mar 23 2011, I need to retrieve the data from last month and the data till todays date(means Mar 23 2011).

If date is Apr 3 2011, data should consists of March month data and the data till Apr 3rd 2011.

Thanks,

Shahsra