DNA Cataloging. Collecting DNA samples for analysis in medical applications and for tracking mutations and disease. You don't end up with as tangible a resource as crystal collecting but it might be a good vehicle for initiating short and long term quests.
To expand on this idea, DNA samples could be used for genetic engineering. Think of it as a similar paradigm to herbalism/alchemy. You collect various gene sequences, and then you can experimentally combine them to engineer new things. Perhaps they could be used to create biological nanobots, anti-virals, personal enhancements, etc.