Personality Models: The Big Five, the Seven Deadly Sins, and?
Depending on your definition of 'personality model' there are plenty to choose from. 

I don't have any good overview of similarities and differences, which are tests more than models, or which are really two names on the same model. 


Big 5/5 factor model. 5x6 axes. Tests include NEO-PI, MMPI-2, IPIP ++.
Global 5. 5 axes
BELBIN 
Emneagram/RHETI
Hexaco
Holland COdes/RIASEC
Jung/MBTI/Kiersey/DISC, 16 PF, MENTI. 4 axes
MOTIV
R-Drive
Temperaments. 4 axes
Hartman. 4 axes
Kolb/Mumford 
Learning styles, Grasha­Riechmann styles, Dunn and Dunn styles, Canfield styles


Which ones you should focus on depends on what you are looking for. 

Big 5\NEO-PI-R is the most scientifically supported model, so I mostly keep to that one. The hard part about Big 5 is the number of traits total (30), which takes a while to really learn, understand and remember. 
MBTI is useful in learning theory about personality types, differences and traits, but it lacks scientific support. 
The others I haven't studied much yet. 

In general I think it's a good idea to use Big 5 as the base, and search for correlations with traits from Big 5.

Sources:

http://similarminds.com/personality_types.html
http://tcc.kcc.hawaii.edu/previous/TCC%202005/santo.pdf
http://www.personalityresearch.org/bigfive.html
http://hexaco.org/scaledescriptions