To get traffic to web site is first task, but often it isn’t enough for services or products providing to end customer. It’s important not only get traffic to your site but also retain your real customers. The question is - how to make them commitment to your product or service?
Offer to people something useful, related to your service. Just to make your service usage more easy and convenient for customers or give something helpful along with your service.
For example, how much time does it take to use your service or just access your site? Is it handy? Quick access to your resources right from web or desktop application on customer’s computer will help easily reach you and will serve as “bookmark” to your page. It will guarantee convenient service delivery and will help make your customer regular. Also, the access button can be provided with your logo. It is one of the ways to advertise your brand through branded software.
Other opportunity is to offer some helpful things, plus to your service. May be, quick web search in well-known search engines or fresh news delivery. Or some useful functions for e-mailing if your customers will access you from e-mail application.
What application to use to place quick access and other functional buttons: web browser, desktop application or e-mail clients? Just depends on your services, your needs and imagination.

Here are more ideas and examples on how to place your service on web browser (Explorer or Firefox) or e-mail client (Outlook or Thunderbird).