List out all MDF and LDF File locations of SQL Sever Databases

SELECT
    db.name AS DBName,
    type_desc AS FileType,
    Physical_Name AS Location
FROM
    sys.master_files mf
INNER JOIN
    sys.databases db ON db.database_id = mf.database_id

Restoring Orphaned MDF File in SQL Server

You can attach the database using CREATE DATABASE FOR ATTACH_REBUILD_LOG.

http://msdn.microsoft.com/en-us/library/ms176061.aspx

If that doesn't work, you can try the undocumented FOR ATTACH_FORCE_REBUILD_LOG.

CREATE DATABASE < YOURDBNAME > ON (FILENAME = 'D:\<YOURMDFNAME>.mdf')
FOR ATTACH_FORCE_REBUILD_LOG

From Management Studio

Attaching the .mdf file through the management console, without a .ldf file

1. right click "Databases" and select attach.
2. Click on "add" and select the .mdf file, click OK.
3. In the details panel select the .dlf file, click remove button.
4. Click the main OK button.