These are all the qualifiers I've come across so far. The first 3 were quite easy to google, but the other 4 have me stumped.
I also can't say I'm completely clear on the nuances of
agg. means aggregate and is used when species have been grouped together.
s.s. stands for sensu stricto and is used for a strict or narrow usage of definition.
s.l. stands for sensu lato and is used for a wide or broad usage of definition. these two pop up a lot in paleontology since species definition can be vague.
cf. stands for "conferre" and is used for provisional names when an organism is not completely known, such as when a variant is found and they are not sure which species to place it in.
cv. stands for cultivar and is usually followed by the unitalicized name of the cultivar.
auct. means "of author" and means the name is used in a different way than it is currently or in a different way than the paper using it does, such as quoting a incorrect name from another author or a debate between two possible usages. (used a lot with overturned or contested names) it is often followed by a qualifier giving more information about usage.
ined. means undescribed, and is used for a new proposed species before it has been formally described (common in paleontology when many papers about the same new specimen may be released at the same conference or where a specimen might not be identified yet still yield useful information in other ways.)
if you put the exact form of the epithet (include the period) followed by the word "species" in google it will usually return the usage, failing that you can search this site.