A number of commercially available products provide libraries for you to reference from your Access projects. You can also find many shared libraries or libraries that are available as shareware. Here are a few resources to get you started. We have not tried all of the controls and libraries found, so we can't endorse all of them.
Access Advisor (http://accessadvisor.net): Search for "ActiveX Control" or search for "DLL." This is a great site for other information, too.
The Access Web (www.mvps.org/access/resources/products.htm): With many resources including ActiveX controls and beyond.
DBi Technologies Inc. (www.dbi-tech.com): Solutions::PIM, Solutions::Schedule, and many more, tested with Microsoft Access.
FMS Inc. (www.fmsinc.com/products): Quite a number of ActiveX controls and add-ins for Microsoft Access.
ID Automation (www.idautomation.com/activex): Barcode ActiveX control and DLL designed for Office programs.
Intuit Developer Network (www.developer.intuit.com): Software Development Kit (SDK) to work with data in QuickBooks.
You should also be aware that many libraries and ActiveX controls that are designed for Visual Basic programming languages can be used by Access. Contact the vendor to find out.