Ways to earn money on the internet if you don't have a website

I found out after visiting a few webmaster forums that they are a lot of people who do not have websites but who earn money providing services to the webmaster community.
Imagine that. These people don't have to worry about paying for web hosting, managing websites and dealing with issues related to maintaining websites. They just provide the services that webmasters need and can earn quite some money by doing this.

Here are a few ways that you can earn money if you don't have a website.

- (Manual) Directory Submissions
A lot of webmasters are looking for people to submit their links to as many web directories as possible. Typically, webmasters do not have too much time to submit their links to hundreds or thousands of web directories as they usually spend their time managing their websites.
You can provide your service to "manually" submit their links to hundreds or thousands of web directories for a small fee. Note that the word "manually" was put between quotes as most people who provide this service do not do the job by hand, one link at a time. Rather, they use tools to automatically submit the links to the web directories.
If you have the time and/or the right tool, you can easily earn around $35 per 500 directory submissions. This is the typical rate that I pay for the service.

- Link Building
This is pretty much similar to directory submissions but the difference is that the links may not necessarily go to web directories.
A webmaster may need x amount of "permanent" links from related webpages and again may not have the time or expertise needed to get these links.
This is where you can come in and earn some money. Your job would be to find webpages and ask their owners to link to your client's sites. You can do so by offering them link exchanges or somehow convincing them to add the links (good luck with that). I am not sure how the link builders do it but if you can figure out how to get a bunch of targeted webpages to link to your client's site, you can earn quite some money for each unique link.
Typically, webmasters would pay you more if you can get links from relevant websites that have a high Google PageRank (PR).

- Writing
If you can write, you will definitly find a huge number of potential web clients who are looking to add fresh content for their websites.
Webmasters are always looking for writers who can write articles, tutorials, or make blog posts related to their websites topics.
You can charge per word or you can charge for each article or blog post.
If you have expertise on a particular field (for example SEO, marketing, web design), then your services can become more valuable to a webmaster and you can charge higher fees.

- Paid forum posting and forum moderation
When a webmaster starts a new forum, he needs to populate his forum with a few threads and posts to jumpstart his online community. Visitors typically do not join and start posting on a forum unless they can see that the forum is active and has useful posts.
In order to get the threads and posts needed to show activity, webmasters hire forum posters. If you have the time, you can offer your service as a paid forum poster. The typical rate is $0.10/post but it could lower if the forum is an easy one to post or higher if the forum requires some expertise to post intelligently.
If you decide you want to be a paid poster, you should resist the temptation to copy threads from other forums and simply repost them on the new forum. It is the easier way to get the job done but if your client notices it, all your efforts will be wasted as you will probably not get paid and will tarnish your reputation.
Also, webmasters who manage large communities often do need moderators to keep their forum free of spam, to move threads to the proper sections, to keep discussions civil and to the topic, and other moderating tasks. If you are interested to become a moderator, contact the administrators of the forums of your choice. Most webmasters would be willing to compensate you for your efforts as a moderator.

These are just a few ways to earn money online that I could think of at the moment. There are many other ways to earn money online by providing services to webmasters.
You may want to visit the marketplace section of popular webmaster forums like digitalpoint.com, sitepoint.com, WebmasterGround's webmaster forum or check freelance marketplaces like project4hire.com to find work.