I'm not going to recommend a company, since I'm writing from Canada, but I trade online exclusively. In addition to being able to do my research while trading, I can also access my accounts by phone or on my blackberry -- this has made my life a lot more flexible (I've done trades while walking in the park with my daughter, waiting for lunch in a restaurant, waiting for flights...)
The degree of risk that you can tolerate should determine which stocks you pick, regardless of your trading method. Trading usually makes up a substantial percentage of my income, but the waters are a little rough now, even for me. Having said that, I like that online trading gives me more control over my accounts and I don't have to get in touch with a broker to put in a buy or sell order.