Well an easy way to check your mails is to use a desktop mail client like Windows Live Mail. But, if you keep surfing the web most of the time using Firefox, WebMail Notifier will do the work for you.
WebMail Notifier is a Firefox Extension which lets you check multiple email accounts simultaneously and it will notify you right in the browser statusbar when you have new unread emails.
this extension currently supports GMail, Google Apps, Yahoo Mail (including Ymail.com & RocketMail.com), Hotmail (including Live.com & MSN.com), Daum.net, Naver.com, Empas.com and Nate.com.And if you want it to show FastMail, Orkut, Lycos Mail then you can configure that using user script
If you are well enough, you can also create userscript for your desired webmail provider. WebMail Notifier works with almost all Firefox versions.
For users with multiple email accounts, this is a great extension. this way you can quickly read your emails and it will save you lots of time.