Here is the list of options that can be controlled using the Spelling preference panel:
Suggestion Mode
There are four suggestions mode: Ultra Fast, Fast, Normal, and Bad Spellers. Here are the descriptions of each mode copied from Aspell manual:
Ultra Fast
This method will use the fastest method available to come up with decent suggestions. This currently means that it will look for sounds-likes within one edit distance apart without doing any typo analysis. It is slower than Ispell by a factor of 1.5 to 2 when a single dictionary is used. Its speed is only minor affected by the size of the dictionary, if at all, but it is strongly affected by the number of dictionary in use. In this mode Aspell gets about 87% of the words from a small test kernel of misspelled words. (Go to http://aspell.sourceforge.net/test for more info on the test kernel as well as comparisons of this version of Aspell with previous versions and other spell checkers.)
This method is like Ultra Fast except that it also performs typo analysis. The typo analysis brings words which are likely to be due to typos to the beginning of the list but slows things down by a factor of about two. This mode should get around the same number of words that the Ultra Fast method does.
This method looks for sounds-likes within two edit distance apart and perform typo-analysis. Is is around 10 times slower than the Fast mode with the English dictionary but returns better suggestions. Its speed is directly proportional to the size of the word list. This mode gets 93% of the words.
Bad Spellers
This method also looks for sounds-likes within two edit distances apart but is more tailored for the bad speller where as fast or normal are more tailed to strike a good balance between typos and true misspellings. This mode never performs typo-analysis and returns a huge number of words for the really bad spellers who can't seam to get the spelling anything close to what it should be. If the misspelled word looks anything like the correct spelling it is bound to be found somewhere on the list of 100 or more suggestions. This mode gets 98% of the words.
Accent Processing

For languages that have accented characters this option defines how Aspell handles such characters:

Do not do anything with accents, i.e., cafe is different from café and only the variant from the dictionary is accepted.
Strip accents
Remove the accents from all words, i.e., cafe is different from café and only the variant without the accents is accepted.
Ignore accents
Ignore accents while checking the words, i.e., cafe is the same as café
Ignore case

Ignore case while checking the words

Allow run-together words

Description forthcoming

Maximum number of words
Description forthcoming
Minimum word length
Description forthcoming

Description forthcoming

skips over quoted text in email messages
skips over HTML tags
skips over TeX commands, parameters, options, and comments. Not all parameters are skipped. For example, Aspell will check parameters of the "\section" command.
skips over URLs, email addresses, and host names