Joel Reyes-Has been writing and developing web sites for several years now, this has lead him to be the creative mind behind Looney Designer a design resource and portfolio site that revolves around web design and development.
In your Gmail, all you have to do is to enter the term size:10mb in the search box and all emails larger than 10MB will show up in the list. You can change the number to reflect the size you want to filter.
This is so far the easiest way to filter your emails by size.