Microsoft has announced that the beta program currently known as Office 12 will become Office 2007 when it is released later this year.
Office 2007 has been completely redesigned compared to its Office 2003 predecessor and features a new "Ribbon" menu system in many Office applications to make editing and navigation easier.

Here's a list of the different Office packages complete with pricing (full/upgrade):

Microsoft Office Enterprise 2007 (Available only through volume licensing; price N/A)
Microsoft Office Professional Plus 2007 (Available only through volume licensing; price N/A)
Microsoft Office Professional 2007 ($499/$329)
Microsoft Office Small Business 2007 ($449/$279)
Microsoft Office Standard 2007 ($399/$239)
Microsoft Office Home and Student 2007 ($149/NA)
Microsoft Office Basic 2007 (Available only through OEMs; price not quoted)

You can read more about it on Microsoft's site (.doc file)

This news article was written on February 16, 2006, quoting Microsoft.