This question have a answer give by microsoft, but the quantity of data you normaly will have to deal in sharepoint 3.0, make you "The new ones" in Sharepoint world a expert, there is real potencial using this webpart, just think real integration "Excel,Sharepoint,Web", in not free version of Sharepoint have a new service call "Excel Services", that substitute Office Web Parts 2003 to 2007, but if you are a sharepoint 3.0 free this can be very usefull.
A good example is connect to Data by ODBC.
To install you will have to make this litle steps and start working:
1. Download the Office 2003 Web Parts and Components add-in. To do this, visit the following Microsoft Web site:
2. Use a file-compression tool such as WinZip to extract the contents of the package that you downloaded. To do this, follow these steps:a. Use the file-compression tool to open the Ststpkpl.exe package, and then extract the Ststpkpl.cab file from the Ststpkpl.exe package.
b. Use the file-compression tool to open the Ststpkpl.cab file, and then extract the following files from the Ststpkpl.cab file to the root of the drive. For example, extract the files to drive C.
Note LocaleID is a four-digit number that represents the locale ID. For example, the locale ID may be 1033.
c. Rename the files that you extracted in step 2b to the following:
• Rename Gplib.cab_LocaleID to Microsoft.Sharepoint.Solutions.GreatPlains.cab
• Rename Quickqt.CAB_LocaleID to Microsoft.Sharepoint.WebParts.QuickQuote.cab
• Rename Microsoft_Office_DataParts.Cab_LocaleID to Microsoft.Office.DataParts.cab
3. Use the Stsadm.exe command-line tool to install the Office 2003 Web Parts and Components add-in. To do this, follow these steps:a. Click Start, click Run, type cmd in the Open box, and then click OK.
b. Type the following lines at the command prompt. Press ENTER after each line.
cd /d %commonprogramfiles%\Microsoft Shared\Web Server Extensions\12\Bin
stsadm.exe -o addwppack -filename Drive:\microsoft.sharepoint.solutions.greatplains.cab -globalinstall -force -lcid LocaleID
stsadm.exe -o addwppack -filename Drive:\microsoft.sharepoint.webparts.quickquote.cab -globalinstall -force -lcid LocaleID
stsadm.exe -o addwppack -filename Drive:\microsoft.office.dataparts.cab -globalinstall -force -lcid LocaleID
c. Type exit, and then press ENTER to exit the command prompt.
4. Restart Microsoft Internet Information Services (IIS) 6.0. To do this, click Start, click Run, type iisreset in the Open box, and then click OK.