Kaplan & First Aid.
I haven't used USMLEworld but I heard a lot of good things about it.
Lots of this is personal preference. Anecdotally I found Crush & Strong Medicine for USMLE III not very effective (though I know several who disagree) because it was too little information, and much of the Appleton & Lange stuff useless.
I was doing questions from A&L USMLE Step II-Internal Medicine book and was getting about 60% of the questions wrong and I thought I was a dead man (at that time I only had a month left before the exam). I then had several IM doctors check out the questions and they told me they couldn't answer half of them either. The book was too hard--& it gave me the biggest mind screw (I almost had a panic attack--I thought I was prepared then this book made me think I was dead).
Some words of advice: Don't gun for the exam if you don't have to, especially if you're a first year. I felt I learned a heck of a lot of medicine after doing my med rotation, and then applying that knowledge to what I did in inpatient psychiatry.
2nd--if you're gunning for USMLE to get a liscence for moonlighting--wait & think. Are you ready to do moonlighting? I didn't think I was ready to do so until the end of my 2nd year. I'm still not doing it now because I didn't take Step III yet (I'm planning on Nov)--but in hindsight--no way was I prepared to do it my first year-especially if doing the moonlighting means you're on your own.