Invoice management is crucial for any small business, but accounting software tends to be expensive and overcomplicated. What if you just need a simple way to log and track invoices? That's InvoTrak in a nutshell. This Web-based tool lets you add one or more clients, then send and monitor invoices to those clients. It keeps a running tally of outstanding and paid invoices and highlights any that are past due (though it doesn't send you e-mail notification, which I think would be a handy feature).
InvoTrak can't generate actual invoices, though you can attach your own (Word files, PDFs, etc.) to the e-mails it sends. Mac users can add an InvoTrak widget to their Dashboard for easier monitoring (now how about a little Windows-widget love, guys?). For a freelancer like me, a service like InvoTrak could really come in handy. It's free and incredibly easy to use. Of course, if you want something a little more robust, check out FreshBooks or Simplybill.