Philip Morris became Altria a few years ago -- they used to own Kraft and some other major brands, but they spun those off.
This site should give you some info about them (click the history link to find when they bought/sold other companies). We had to read the first 3 chapters of
The Corporation for our business class -- it had some interesting arguments about corporate ethics -- it might give you some food for thought if you could find it at your library (or a local college library -- I was able to skim it in about half an hour).
Is your presentation on unethical practices or products? If it's practices, you don't have to limit yourself to tobacco companies -- try googling "corporate scandal" and you'll see what I mean. There was the whole accounting debacle (Enron, Worldcom) that brought about the Sarbanes-Oxley act, the subprime mess, lawsuits over marketing bad foods to kids (Kraft was in the thick of that one, as well as McDonald's), environmental impact issues, etc. Wal-mart's had a ton of issues, too -- discrimination, illegal workers, fair wage, predatory pricing...
If you want to stick to companies that sell vices but also other products under different brand names, try going directly to the corporate websites (of the parent company) -- under their "about" or "for investors" sections, they should have info about their brands. To find the parent company, the same areas should have the parent company name for any individual brand you look up. Shapu mentioned RJ Reynolds; they and Philip Morris are the 2 big tobacco companies left. Other vice industries include gambling (Harrah's is the only company I know of -- I'm not a gambler (or a smoker)). Gun companies might be owned by larger corporations, but I know even less about guns than gambling.
After the tobacco lawsuits, tobacco companies divested of their other businesses to protect them from the lawsuits (the US suits are mostly over, but they're still going on in other countries). Philip Morris actually has commercials here encouraging smokers to find out how to quit at their website. The smoking market is shrinking in the US but growing internationally, especially in developing countries. In the US, smokeless tobacco is growing, as are smoking cessation products (the ones containing nicotine are often manufactured by the tobacco companies).
I hope at least some of this info is useful.