Freelancing is a tough gig.  The actual work itself may not be the really hard part and in fact it’s often enjoyable since it’s what you may love to do.  But getting out there and finding clients to do the work for may be the really tough part. 

It’s also sometimes hard to get your clients to pay you for the work you’ve done.  Being organized and running your freelance operation like a real small business will help you make more money, get paid on time, find more work, and generally feel better about yourself and your professional life.

One of the best things you can do for yourself in terms of professionality (and income) is to invoice your clients properly and efficiently.  

Small Business Trends has a list of 30 Online Invoice Apps for Small Business that may be helpful to you.