Need to send an invoice for some freelance work you've done? Don't want to bother with a complicated Excel spreadsheet based invoice?
Great news! I've compiled a list of the best Web based invoicing tools for freelancers. While the list was created with one-person freelancing businesses in mind, the services can be useful for small service firms or anyone who wants to request and collect money online.
I especially want to point out two sites: Billing Manager and FreshBooks.
1. A free plan that is actually useful. Intuit offers a powerful solution in Billing Manager that is free forever -- even as the volume of your invoices and clients increase. The catch is you can't automatically accept PayPal payments, and they are constantly but unintrusively reminding you of Merchant Service (their online credit card processing service). In my experience, it also feels a bit slower than the paid services.
2. Inexpensive, easy to use, yet very powerful. If you don't mind paying for a better user experience, FreshBooks is easy to use, has built-in time tracking, and supports multiple users (your staff). It's a bit pricier than comparable services (eg., Blinksale, SimplyBill), but the difference in ease of use and features is significant. (Blinksale might be too simple for some; SimplyBill is cheaper but its user interface could be easier to use.)
Read more: Web-based Invoicing Apps for Freelancers

you can also take a look at http://www.SalesKing.eu, it`s a new invoicing app. At the moment SalesKing is in closed beta, but feel free to request for an invite.
Another web based invoicing solution is http://www.inlattice.com. In addition to web based invoicing solution, inlattice works well with QuickBooks invoices. No data entry is required if you are a QuickBooks user.
I am currently working on online invoicing application i.e. http://www.invoicera.com. The application is currently in the pre launch stage. it is a simple to use application and at the same time very effective. If anyone wants to have a try then you can register on the website.
Check out http://www.FastDue.com. Invoicing is even easier to use than FreshBooks and is completely free.
Plus you can create business agreement forms, send them, and sign electronically –all online.