You can use the demo site at
http://demo.moodle.org/
I'm also doing an MSc in Learning and Technology (in TCD) and recently did a paper on LMS
usability.
Some references I found useful are:
Bremer, D., & Bryant, R. (2005). A Comparison of Two Learning management Systems: Moodle vs Blackboard. Paper presented at the 18th Annual Conference of the National Advisory Committee on Computing Qualifications, Tauranga, New Zealand.
Di Iorio, A., Feliziani, A. A., Mirri, S., Salomoni, P., & Vitali, F. (2006). Automatically Producing Accessible Learning Objects. Educational Technology & Society, 9(4), 3-16.
Graf, S., & List, B. (2005). An Evaluation of Open Source E-Learning Platforms Stressing Adaptation Issues. Paper presented at the Fifth IEEE International Conference on Advanced Learning Technologies (ICALT), Kaohsiung, Taiwan.
Machado, M., & Tao, E. (2007, October 10 - 13, 2007). Blackboard vs. Moodle: Comparing User Experience of Learning Management Systems. Paper presented at the 37th ASEE/IEEE Frontiers in Education Conference, Milwaukee, WI.
Martin, L., Martínez, D. R., Revilla, O., Aguilar, M. J., Santos, O. C., & Boticario, J. G. (2008, 6-7 November). Usability in e-Learning Platforms: heuristics comparison between Moodle, Sakai and dotLRN. Paper presented at the 7th European Conference on e-Learning (ECEL), Agia Napa, Cyprus.
Neilsen, J. (2003). Usability 101: Fundamentals and definitions-what, why, how? Retrieved 20/11/2008, from
http://www.useit.com/alertbox/20030825.html
Nielsen, J. (1994). Ten Usability Heuristics. Retrieved 16/11/2008, 2008, from
http://www.useit.com/papers/heuristic/heuristic_list.html
Pierotti, D. (1995). Heuristic Evaluation -A System Checklist. from
http://www.stcsig.org/usability/topics/articles/he-checklist.html
Rusama, M. (2006). Microsoft Word template for making Moodle questionnaires in GIFT format. from
http://www.soberit.hut.fi/sprg/resources/moodle/GiftConverter.html
Yatskovsky, V. (2006). Microsoft Word template for making Moodle quizes. from
http://www.finemetronome.com/moodle/