Database with many publication, How to make snapshots for publications run faster
Here is one thing you can do to keep your database from getting pegged while a snapshot is in place:


Set up master -> slave replication. 
Use the slave replica for snapshots.


If you were to provide the flavor of SQL you are using as well as what mechanism you are using to create snapshots (i.e Xen, AWS, etc.), I might be able to provide a bit more context.