The most popular online vocab learning tool is probably Quizlet - client software is available for most platforms as well as their being a capable web site. Let me know if you find anything better. I've added a few sets and will continue to do so: see http://quizlet.com/olops.

Please search Quizlet for your course level but here are a few users who have contributed Welsh sets for starters:


Uwch 1

Uwch 2

Uwch 3

Uwch 4

Uwch 5