If you are using eclipse, then you should download the maven plugin from sonatype here http://m2eclipse.sonatype.org/.
This comes with a useful graphic visualisation of your dependencies (in particular transitive dependencies - dependencies you have not explicitly defined in your POM), and also shows conflicting dependencies.
Update: from the comments below, your mileage may vary.
One thing that I've found challenging is determining what is in each package, especially from Spring.
To that end, I've found Netbeans' support for maven to be outstanding in how it lets you know what libraries are pulled in by each requirement. 6.7 Beta contains a graphical tree which is outstanding, and m2eclipse also has a very nice graphical dependency tree. How else would you know that spring-orm includes, spring-beans, spring-core, spring-context, and spring-tx? You can ask maven for the dependencies using the dependency plugin from the command line, but the graphical representation is quite handy. dependency:tree is the goal you want to run. Obviously you can also run that from Netbeans or Eclipse.
So, as an example of one of your collisions:
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-annotations</artifactId>
<version>3.4.0.GA</version>
</dependency>
actually includes hibernate-commons-annotations-3.1.0.GA not 3.3. It also includes hibernate-core-3.3.0.SP1, not 3.3.1.GA.
I would start at your "biggest" component, and start to see what parts that already includes and only add what is missing. Even then, double check that you don't have a duplicate dependency and if need be, exclude the duplicate as shown in the answer to this question.