That's a pretty open ended question. I mean, it depends on how deep you want to get into it, and what you want out of it. I mean, sure, you can play D&D, but if nobody's interested in the campaigns, you're gonna be lonely come game night. If you want something a little more story driven, you might want to consider World of Darkness/White Wolf games [Vampire the Masquerade, Werewolf the Apocalypse, and so forth]. If you want more technical rules but wanna ditch the fantasy setting, you could go with d20 Modern/Future, or go futuristic with simpler rules and go with Shadowrun, which [at least 4e] only uses d6.
Once you decide what you and your friends want from the gaming experience, then it's time to get what you need. Some games require/recommend the use of miniatures, while others don't. Unless LARPing [Live Action Role Playing--Youtube/Wiki it to see what I mean], you're gonna need dice, which you can get at an hobby store. I've always found it good to have more than one set, just in case. A personal touch I like to use when I'm storyteller/DM is I like to have a CD with me of different songs for different occasions to kinda help set the pace; a chase or battle would have a fast song, whereas drinking in the pub you'd hear the local musicians play their songs.
If you just want to play straight D&D, all you really need are the source books [Player's handbook, Dungeon Master's Guide, and the Monster Manual], dice, and some printed out character sheets, which are found in the back of the PHB.