Suppose you have a DBF (.dbf) file containing X and Y values that you want to import and save as a spatial layer.
QGIS doesn't support direct import of a DBF file as a map layer, however, we can use some command line magic to convert it to a CSV file and then use the Delimited Text plugin to get the job done.
Your DBF file should have an id for each record and fields containing X and Y values. If it has additional fields that should be OK as well.
First convert the DBF to a comma delimited file using ogr2ogr:
ogr2ogr -f CSV my_csv my_data.dbf
If you don't have ogr2ogr see http://www.gdal.org/index.html.
This will create mydata.csv in the mycsv directory. You are now ready to bring it into QGIS.
Here are the steps to import the CSV:
If not already enabled, use the plugin manager to enable the Delimited Text plugin
Click on the Delimited Text icon in the Plugin toolbar or choose it from the Plugins menu
Browse to the location of your CSV file
Enter a name for the layer
Under Selected delimiters, check Comma
If your X and Y fields aren't automatically determined, set them using the drop-down boxes
The sample text should show how the file is being parsed---if it looks right click OK, otherwise adjust the settings
The layer is added to QGIS
At this point the layer behaves pretty much like any other QGIS layer. To save it as a shapefile, right click on its name in the legend and choose Save as...