I know this is an old thread but it make be worth mentioning that these jars are now included in the eclipse Android ADT bundle (for MAC anyway, I have not checked for Windows). You do need to check the version is the one you want, but if it is you are good to go.
This means you can add them to your project without having to download them separately first - just follow these steps:
First right click your project and select properties as shown below:

Then select Java Build Path from the pop up window:

and now select the 'Libraries' tab:

and click on 'Add external JARS' and navigate to your ADT bundle/sdk/tools/lib/httpclient (httpmime etc), and then just click open:

You also need to import the Jar file itself into your project. I found the best way to do this was to simply copy the JAR files into the 'libs' folder in your project - i.e. CTRL C and CTRL V, or normal drag and drop file copy. To be safe I would refresh (right click project and select refresh - see menu in first picture above) and then clean your project.
Note if you do the Build Path part above correctly but forget to add the JAR files themselves into your 'libs' folder, you will get an error like:
'Caused by: java.lang.NoClassDefFoundError: org.apache.http.entity.mime.content.FileBody'.
To resolve this just copy the jar files into the 'libs' folder in your project.
You should now be good to go!