
One of the best things you can do is make sure that you're maintaining a proper and up-to-date list of your clients and their contact information. If you're not already, consider using a service like Mailchimp, which offers an easy way to keep track of client information, and lets you reach out them. Old clients can be one of the best ways to generate new business, and some of them may even be interested in repeat business. Reach out and inquire how their current projects are going, and share some of your own current work. Keeping your name in the forefront of their minds is one of the best ways to ensure that they'll recommend you to others or re-hire you for new projects.
Another great way to start generating some additional revenue is to look at your informational assets and think about ways to monetise them. You've probably got a fair amount of reusable code that might be worth something to others, if you were to package it carefully and sell it. Alternatively, you could distribute it under a Creative Commons or GPL license and use it as a method of developing a name for yourself in the programming world - everyone always loves free code. Just make sure to document all the various functions as clearly as possible!
If you're looking to expand your horizons, you might want to use the time to make sure that you're up-to-date about any and all developments in the world of web development. As we all know, things change at an incredibly rapid pace, and it's easy to lose track of new developments when you've been finishing up a project with some marathon coding sessions. The more up-to-date you are, the more impressive you'll be to potential clients who are looking for cutting edge solutions.
Finally - and bear with us here, we know it's not popular - there are the ever-necessary backup and bookkeeping tasks. While they're not popular, they certainly are essential for freelance coders. We've heard many stories from freelancers who have been so swamped with work that their invoicing has fallen off, and they have outstanding money owed to them. A simple followup email is usually enough to get past clients to pay their bills, and otherwise you're simply leaving money on the table that you've already earned. That prospect alone should be enticing enough to make you break out the dreaded accounting software!
Hope the above helps. Whilst it's not directly linked to our PHP encoder we thought we’d share it with you in the first of a series of more general development and business-focused articles.