Legal advice
Very early on, you'll want to select legal counsel for your company. There are many law firms in the Portland area that serve emerging companies. (There's a list in the Service Vendors section of OregonStartups.com.) You'll notice in many of the items on the checklist below, you'll see phrases like "get advice from your legal counsel". There are many legal questions that come up, and many legal documents to deal with over the life of a startup. You need a lawyer.
Law firms that work with startups realize that prior to receiving funding, there may not be cash available to pay for legal services. So frequently, they are willing to delay billing you until some significant investment event occurs. That doesn't mean the clock isn't running: it is. Typically, you will not receive an invoice until a funding event happens. That means you won't have any idea of how fast the legal bill is increasing in size. Suggestion: ask for a monthly summary of the hours and total fee that is accruing. It's better to know than to get a nasty surprise late in the game.
Some law firms may be willing to charge a lower fee in return for equity (stock) in your company. That's worth exploring. Some of the larger firms also have a small investment fund that allows them to make investments in their startup clients, so you can also explore that possibility.
Financial and Accounting advice
You'll also need accounting advice. If your team already includes a finance person, then perhaps he or she already has the right connections to accounting firms that work with startups. (You do want a firm that has experience with high-tech startups.) Aside from getting general advice, you'll need an accounting firm to prepare your company's taxes. Also, it is likely that your investors will require an annual financial audit, which also requires an accounting firm. Some local firms are listed under Service Providers.
Other Service Providers
You may also need the services of other types of service providers. There are companies who can help outsource everything from the CFO function (a part-time "contract Chief Financial Officer"), to account services, Human Resources (HR) services, marketing, public relations (PR), payroll, real estate services (to help you find office space), etc.