Reddit reviews Callen's Ultrasonography in Obstetrics and Gynecology

I'm not sure what level your skills are. Most of the best online resources come from the EM side, and those limit themselves mostly to the basics of OB and pelvic ultrasound.

OSU is pretty well known for their ultrasound curriculum, and has a nice website. Like I said - limits itself to the basics. They also have an app for iPhone that's actually really good, too, and walks you through the exams.

Mount Sinai has probably a better website and even has an algorithm for the EM physician to use for a pelvic ultrasound. But I don't know if that's sufficient for what you might be looking for.

As far as textbooks, the standard in EM is Ma and Mateer's. But the info in it is essentially as found above, if a bit better and fleshes it out significantly, but still. If you're looking to be hands-on with the (transabdominal) probe and buy a butterfly and do things yourself in office, maybe this is exactly what you need.

But I anticipate that you might need a more OBGyn focused reference text like the School Textbook of Ultrasound in Obstetrics and Gynecology. Or Callen's Ultrasonography in Obstetrics and Gynecology, which is a bit more robust.

My preferred general textbook is "Textbook of Diagnostic Ultrasonography" by Hagen-Ansert, and for more detailed OB/Gyn ultrasound I love the "Ultrasonography in Obstetrics and Gynecology" by Callen.