key components are

The extent to which

features tobe tested

features  not to be tested

Feature pass/fail
test envirornment
testing approach
suspension criteria

Along with above some others are there 
1) Risk 
2) Test Schedule
3)Control Procesure like bug Review meeting, change request,
defect reporting.

Along with above some others are there 
1) Risk 
2) Test Schedule
3)Control Procesure like bug Review meeting, change request,
defect reporting.

In addition to the above components the factors like:

1.Unforeseen problems that means we have to guess certain 
problems that may arise in client's place.
2.Scheduling and allocation the testing resources
3. HW/SW requirement.
4.In additon to Risks, failures to be identified like HDD 
crash, DB recovery, back ups needed in terms of HW/SW and 
resources to be planned in advance!

following are thekey components in test plan
1.introduction
2.scope&objective
3.testplan id
4.list of features
4.1features to tested
4.2features not to tested
5.test approach
6.test environment
7.entry criteria
8.suspention criteria
9.exit criteria
10.test deliverables
11.staffing needs
12.roles and resposibilities
13.training needs
14.communication & status reporting
15.schudule
16.approvals
if any thing is more pls give me feed back.
thank you.

14.communication & status reporting
will not come under Test Plan as per IEEE 829 standard.