I tried aptana - found it took over my whole eclipse environment and put news feeds and other rubbish all over the place...
I then tried installing a subset of the aptana jar's and ended up pretty happy with the result.
Here's what I have in my plugins directory:
com.aptana.ide.core_1.2.0.018852.jar
com.aptana.ide.snippets_1.2.0.018852.jar
com.aptana.ide.core.ui_1.2.0.018852.jar
com.aptana.ide.debug.core_1.2.0.018852.jar
com.aptana.ide.editor.css_1.2.0.018852.jar
com.aptana.ide.editor.html_1.2.0.018852.jar
com.aptana.ide.editor.js_1.2.0.018852.jar
com.aptana.ide.editors_1.2.0.018852.jar
com.aptana.ide.editors.codeassist_1.2.0.018852.jar
com.aptana.ide.epl_1.2.0.018852.jar
com.aptana.ide.io.file_1.2.0.018852.jar
com.aptana.ide.jface.text.source_1.2.0.018852.jar
com.aptana.ide.lexer_1.1.0.018852.jar
com.aptana.ide.libraries_1.2.0.18696
com.aptana.ide.libraries.jetty_1.2.0.018852
com.aptana.ide.logging_1.2.0.018852.jar
com.aptana.ide.parsing_1.2.0.018852.jar
com.aptana.ide.search.epl_1.2.0.018852.jar
com.aptana.ide.server_1.2.0.018852.jar
com.aptana.ide.server.core_1.2.0.018852.jar
com.aptana.ide.server.jetty_1.2.0.018852.jar
com.aptana.ide.server.ui_1.2.0.018852.jar
..and in the features:
com.aptana.ide.feature.editor.css_1.2.0.018852
com.aptana.ide.feature.editors_1.2.0.018852
com.aptana.ide.feature.editor.html_1.2.0.018852
com.aptana.ide.feature.editor.js_1.2.0.018852