Yes, I've done it a few ways. The safest way to do this is using the webservices Magento exposes to query objects programmatically. This will insulate you from database-level changes (such as the flat product catalog, a recent addition).
Failing that (if the performance of the webservices doesn't meet your needs), you can reconstruct the catalog data from the database directly. Use the following tables (assuming you're not using the flat catalog):
eav_entity_type
eav_attribute
catalog_product_entity
catalog_product_entity_int
catalog_product_entity_varchar
catalog_product_entity_text
catalog_product_entity_decimal
catalog_product_entity_datetime
You'll want to read up on EAV models before you attempt this. Bear in mind that this is largely the topic over which people call Magento complicated.
Hope that helps!
Thanks,
Joe