This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
1) I don't think that such dependency is really an "attribute" of a class (in terms of UML). I would show it as an "aggregation".
2) The purpose of any UML diagram is not show "everything you can show". The purpose is to inform the reader about your architectural decision, at some certain level of abstraction. If all your dependencies belong to the same level of abstraction and you can't place them all into an easy-to-read UML diagram - it's a sign of poor design. Re-design your architecture for better cohesion and less coupling.