In MOSS 2007,there's 9 Master Pages built-In on any create site in Sharepoint 2007.
The Question is : Which Master Pages shall I use for my Site ?
Case #1: Blue Vertical / Black Vertical
This is the best choice in case you are building an internet sites with good representations of the WCM related columns,No Top Navugation only Left Navigation which is most required on internet sites.
Case #2: Blue Tabs
Is the best alternative for default master page .The difference is the tabbed representations of the top navigation.
Case #3: Blue Band / balck Band / Blue Glass Band
Same as Default master page with both Top and Left navigation,the best selection for starting to customize the default master page.
Orange Sigle Level & Black Single Level : same as blue band master pages with different on Color Combinations.
Or you can still use the default master page with full control on the top and left navigation and customize it but it will take much work on your customizations.
The Good starter from my point for your customization is Blue Band Master page coz it contains the minimal that u want to put on your master page with site actions and navigation.
Hope this Tip help.