using iPhone as a wi-fi hotspot

Mobile broadband dongle or three mifi does job much better imo

You can either pay for "tethering" which is expensive OR you could "jailbreak"the iphone which means you could tether it for free to the laptop and any data allowance just comes through your iphone data allowance..You could try typeing "tethering and jailbreak iphone" into google..

pda net best for iphone tethering! must be jailbroken though

You can now set up a personal hotspot on your iPhone 4

http://support.apple.com/kb/HT4517

Warning: you may incur higher data charges

Or you can use an Android 2.2 (froyo) on it and just tether directly from that. Most networks have a fair use policy but unless you're really caning it with streaming media then you should be okay as they normally come in at around 500mb a month.