We have a very large table (> 77M records and growing) runing on SQL Server 2005 64bit Standard edition and we are seeing some performance issues. There are up to a hundred
Standard should be able to handle it. I would look at indexing and the queries you use with the table. You want to structure things in such a way that your inserts don't cause too many index recalcs, but your queries can still take advantage of the index to limit lookups to a small portion of the table.
Beyond that, you might consider partitioning the table. This will allow you to divide the table into several logical groups. You can do it "behind-the-scenes", so it still appears in sql server as one table even though it stored separately, or you can do it manually (create a new 'archive' or yearly table and manually move over rows). Either way, only do it after you looked at the other options first, because if you don't get that right you'll still end up having to check every partition. Also: partitioning does require Enterprise Edition, so that's another reason to save this for a last resort.