Things tried: Go to Install New Software -> Selected C/C++ development tools. I get the following error
Cannot complete the install because of a conflicting dependency.
Software being installed: C/C++ Development Tools 8.0.0.201106081058 (org.eclipse.cdt.feature.group 8.0.0.201106081058)
Software currently installed: Aptana Studio 3 3.0.4.201108101506-10082011150838 (com.aptana.rcp.product 3.0.4.201108101506-10082011150838)
Only one of the following can be installed at once:
Debug Core 3.7.0.v20110518 (org.eclipse.debug.core 3.7.0.v20110518)
Debug Core 3.6.0.v20100519 (org.eclipse.debug.core 3.6.0.v20100519)
Cannot satisfy dependency:
From: Aptana Studio 3 3.0.4.201108101506-10082011150838 (com.aptana.rcp.product 3.0.4.201108101506-10082011150838)
To: org.eclipse.debug.core [3.6.0.v20100519]
Cannot satisfy dependency:
From: C/C++ Development Tools Debugger UI 7.1.0.201106081058 (org.eclipse.cdt.debug.ui 7.1.0.201106081058)
To: bundle org.eclipse.debug.core [3.7.0,4.0.0)
Cannot satisfy dependency:
From: C/C++ Development Tools 8.0.0.201106081058 (org.eclipse.cdt.feature.group 8.0.0.201106081058)
To: org.eclipse.cdt.platform.feature.group [8.0.0.201106081058]
Cannot satisfy dependency:
From: C/C++ Development Platform 8.0.0.201106081058 (org.eclipse.cdt.platform.feature.group 8.0.0.201106081058)
To: org.eclipse.cdt.debug.ui [7.1.0.201106081058]
Make sure the plugin you are trying to install (C/C++ Development Tools) is intended for the version of Aptana/Eclipse you are using. The version of Aptana you are using seems to depend on Debug Core 3.6.0.v20100519 (org.eclipse.debug.core 3.6.0.v20100519), while the version of the dev tools plugin you are installing depends on org.eclipse.debug.core [3.7.0,4.0.0), hence the conflict you are getting. Try to install an older version of the dev tools plugin that is intended for Eclipse Helios (3.6.), and not Eclipse Indigo (3.7.).
Good luck.