With all due respect, I don't think the previous respondent understood the question. The gentleman is correct as far as one of the functions of a registered agent in Nevada (and generally all jurisdictions) is receiving service of process, however he is incorrect in his suggestion that the Secretary of State could act as registered agent as an alternative to you selecting a private agent commercial or non-commercial in Nevada. In Nevada this is not an option. If you have no agent designated in Nevada, your entity status will be defaulted and eventually revoked.
The difference between a commercial and non-commercial registered agent is that a commercial registered agent has generally registered with the state as same, and has agreed to meet certain criterion to be able to say they are a commercial registered agents. A lot of states have this designation available. It is safe to suggest that you would always want to choose a commercial registered agent over a non-commercial registered agent.
Additionally, the article he referred to about why not to form a LLC in Nevada is also largely incorrect. Using the arguments in that article, nobody should incorporate in Delaware if they aren't doing business in Delaware, and as we know, a LOT of people incorporate in Delaware.
There are plenty of strategies for utilizing Nevada, Wyoming, and other state tax free jurisdictions for your business, but you have to know how to use them, and they are not a one-size-fits-all solution. Nevada is great for holding intellectual property that receives royalties, or I would say for a majority of internet based companies.
If you operate and live in an extremely highly taxed state such as for instance California, you can have your main operating company registered in California and another company in Nevada that owns your office equipment, vehicles, intellectual property, etc. and leases it to your California company at whatever rate you agree to, thus draining the profit out of your California company so that you only pay minimal California state taxes. Tens of thousands of companies in California employe this and similar strategies. Many California companies are only able to be in business because they employ a strategy such as this. There is an excellent article explaining this (Dual Entity Strategy).
The reason I would hesitate incorporating in Nevada is because of the onerous and exorbitant license fees they pile on to the already high annual list filing fees. The legislature in Nevada is loaded with public employees and other legislators beholden to public employee unions, so following the lead of California, they have been mismanaging the state's finances for years, have massive unfunded pension liabilities, and some legislators have publicly declared their desire for a business tax, so any advantage to doing business in Nevada might be a short-lived proposition.
As for registered agents, there is a company that does a year of free agent service in any state (Free Registered Agent), and for more general information about registered agents, there is an excellent article by Jennifer Reuting, the author of Limited Liability Companies for Dummies (Registered Agents)