I want to study Sharepoint. But if I create a project in VS 2010 it will shows an error message like "Sharepoint server is not installed in this machine". So is there any free Sharepoint server or service available? Is there any other way to start learning sharepoint 2010.
SharePoint is a very demanding platform to work with, ensure you have hardware matching the specifications, http://technet.microsoft.com/en-us/library/cc262485.aspx.
Working with crappy hw, virtual drives and so on will cause a lot of pain and consume loads of time. Think of learning SharePoint and SharePoint development as an investment.
However, if you just want to play with it for a bit follow this guide for installing SP on Windows 7 http://msdn.microsoft.com/en-us/library/ee554869.aspx
It do require x64
Download SharePoint 2010 Foundation since it's free. http://technet.microsoft.com/en-us/sharepoint/ee263910.aspx#tab=1
Cloudshare (www.cloudshare.com) is the easiest and fastest way to get setup using SharePoint. It's about $60/month, but you get a machine pre-installed with SharePoint, SQL Server, and Windows Server. All you need, and you don't have to do a thing!
Also, if you're looking for something a bit cheaper, try Office365 w/SharePoint. It won't give you every feature, but it's less than $10/month per user, so it might be what you're looking for?
Two avenues to try:
Free sharepoint service: http://www.freesharepoint.com/
Trial Sharepoint 2010: http://sharepoint.microsoft.com/en-us/Pages/Try-It.aspx
Have a look here. There are VHDs available for download to have a play with.  If you can't find your way around VHDs best place to start would be getting your hands on WSS4 (Microsoft Sharepoint Foundation). WSS is a free version of sharepoint as opposed to full whack MOSS (Microsoft Office Sharepoint Server) and a good place to start playing.
I highly recommend SharePoint 2010 Developer Training Course from Microsoft.
A SharePoint development rig can be pricey. Check out the free trial at cloudshare.com. money well spent...currently 49 a month.. Removes the headaches of maintaining the environment so u can focus on Dev work.
As mentioned in the other posts you should have a look at MSDN to get started with the SharePoint Framework itself.
Cloudshare.com is offering SharePoint developer systems hosted in the cloud. There is a 14 day trialversion.
Cloudshare is great, it's fast and it's offering a lot of templates for SharePoint developer Farms.
One of the best books for SharePoint development is "Inside Microsoft SharePoint" from Microsoft Press.
NothingButSharePoint.com is also a great point to get started with SharePoint regardless to your profession. There is a lot of content for Users/IT-Pros/Developers
There is a really useful script which helps to setup all the environment you need to start development for SP (SP2010 trial, VS, SPD, Office and so on). So, you can just start it, enter some input details and right after it finishes you can start development.
It is absolutely free (if my memory serves me well, it is 180 days trial). I highly recommend it for quick start.
SharePoint 2010 Easy Setup Script