Medicines for nausea are known as antiemetics and there are many out there but they fall into a couple basic categories.
First we have drugs like Zofran (ondansetron), which is often used for chemotherapy induced-nausea works on seratonin in the CNS and GI as an antagonist.
Dopamine agonists are very common and include the antipsychotics as was mentioned and specifically one AP that is commonly used as an antiemetic is compazine (prochlorperazine). These are effective but have nasty side effect profiles.
The common OTC motion sickness meds are all antihistamines like dramamine (dimenhydrinate which is very similar to diphenhydramine) and Meclizine (sold as Bonine or Dramamine II which is similar to cyclizine).
Then of course we have the cannabinoids and their antiemetic properties are well known and discussed above.
Anticholinergics were historically used for nausea and share many properties with the old antihistamines like dramamine and benadryl.
Promethazine is interesting because its an antipsychotic with anticholinergic effects and is probably the most common antiemetic combined with codeine due to relief of nausea, synergistic effects and a tolerable side effect profile.
Choosing an antiemetic depends on a lot of factors and that's why there are so many that have such drastically different mechanisms of action. Different side effect profiles, legalities (cannabis), indication and Rx vs. OTC status factor in the decision of which is optimal.