At this point, the iPhone is such a phenomenon that there's no shortage of resources for getting more help, news, tips, and information. Here are a few examples:
Apple's Official iPhone User Guide. No, it doesn't come with the iPhone. But yes, there is an actual downloadable PDF user's manual. http://manuals.info.apple.com/en/iPhone_User_Guide.pdf
Apple's Official iPhone Help Web Site. There's a lot going on here: online tips, tricks, and tutorials; highlighted troubleshooting topics; downloadable PDF help documents; and, above all, an enormous, seething treasure trove of discussion boards, where ordinary iPhone owners complain and solve each other's problems. www.apple.com/support/iphone/
Apple's Service Site. If the thing is really, truly broken, this site lists all the dates, prices, and expectations for getting your iPhone repaired. Includes details on getting a replacement unit to use while yours is in the shop. www.apple.com/support/iphone/service/faq/
iPhoneBlog. News, tips, tricks, all in a blog format (daily posts, with comments). www.theiphoneblog.com/
iLounge. Another great blog-format site. Available in an iPhone format, so you can read right on the device. www.iLounge.com/
MacRumors/iPhone. Blog-format news; accessory blurbs; help discussions; iPhone wallpaper. www.macrumors.com/iphone/
iPhoneAtlas. Discussion, news, applications, how-tos. www.iphoneatlas.com
Gizmodo. Snarky, funny, sometimes raunchy—the commercial bloggers' take on the iPhone. www.gizmodo/iphone