SQL Server does not have a true way to scale out. The most you might be able to do is offload some read activity to a mirrored copy of the database, if you are using SQL Server 2012 and Always On, this read only copy is not available in any other version. . Or you could use replication to offload the reads to another copy of the data that you need, replication is available in earlier versions.
The other thing you could look into if you truly need to scale out and have multiple servers that are able to write to a single database is Peer to peer transactional replication. But make sure you do your due diligence here and test. Here is a link for you to check out.
http://technet.microsoft.com/en-us/library/ms151196.aspx
Other then those limited options, I think that the best bet is to scale up. Bigger server more resources, faster disk, things like that.