Amir,
MyEclipse provides a polished UML2 tooling experience. With support for Drag-and-Drop reverse engineering, Import and Export of XMI 2.1 & 2.0 files, Rational EMX file support and advanced diagram layout, MyEclipse provides all the UML2 modeling support you’ll need for your projects. You can find MyEclipse UML tutorials under Help > Help contents > MyEclipse Learning Center > Developing UML1 models / Developing UML2 models.
Regarding ObjectAid plugin, you can install this plugin in MyEclipse for spring 10.6 by following these instructions :
1. Goto Help > MyEclipse configuration center > Software and click Add Site.
2. Enter the following name and URL and click Ok
Name: ObjectAid UML Explorer
URL: http://www.objectaid.net/update
3. Once you press “OK” you’ll return to the Software tab. Next, expand the update site you just added and select the plug-ins you’d like to add to MyEclipse by right-clicking on each of them and selecting “Add to profile…”
4. After adding the plug-in to the profile you’ll see it listed as a pending change. Once all your changes are complete, select the “Apply changes…” button to download the software, accept any additional license agreements, complete the installation, and restart MyEclipse.
Hope this helps.