Most companies can obtain an EIN online here.
Note that in order to obtain an EIN online, the person applying on behalf of the company (who the IRS calls the "responsible party") must have a taxpayer ID with the IRS.
Also note that the company's address for the EIN application is the address of the company's principal place of business -- in other words, the address of the company’s headquarters or nerve center (the place where the company’s officers direct, control, and coordinate the company’s activities). For a startup that does not yet have an office, this is often the home address of one of the founders. The company's address is NOT the address of the company's Delaware registered agent.
If you are unable to obtain an EIN online, you'll need to use another method, described here.
The fastest offline method of obtaining an EIN is likely to be via telephone - call either 1-800-829-4933 (US applicants) or 267-941-1099 (international applicants). They will give you a fax number so that you can fax in a completed Form SS-4.
Since there may be some hold-times when calling the IRS, we recommend downloading and filling out the Form SS-4 ahead of your phone call. That way, if you have any questions about filling out the form, you can get them answered in one phone call. Note that the instructions for the Form SS-4 contain answers to many common questions.
This blog post and its comments may also be informative.
The IRS has a FAQ about obtaining EINs online.
If you have any further questions about EINs, please contact the IRS at 1-800-829-4933 (US applicants) or 267-941-1099 (international applicants).