Kirsten,
Until you reach those 50 posts (which I am trying to get to also.

) you can use docstoc.com. They have lots of templates you can use.
As for invoices, I use QuickBooks Pro. It is awesome! I am starting to do bookkeeping for my clients, which is a popular interest in my area. If you can afford it, the software definitely saves a lot of retyping and manual calculations down the road.
If not, docstoc.com probably has templates for invoices too.
Hope this helps!