www.gamefaqs.com is probably the best bet.
Some fighting games are less combo dependant than others; Street Fighter 2/3 and Virtua Fighter series tend to go for a more chess like tactical play where timing is most important.
Stuff like Killer Instinct, Street Fighter Alpha series and Tekken are more dominated by long combo strings, not something I'm a big fan of.
But anyway, Gamefaqs is really handy because there are some seriously odd fighters out there like Rage of Dragons for the Neo Geo that even seasoned fighter fans are going to have trouble with.