Personal pronouns (like I, we, and you) are important in letters and memos. In such documents, it is perfectly appropriate to refer to yourself as I and to the reader as you. Be careful, however, when you use the pronoun we in a business letter that is written on company stationery, since it commits your company to what you have written. When stating your opinion, use I; when presenting company policy, use we.
You can also include links to online portfolios, if appropriate, or a link to your professional social media account such as LinkedIn or Twitter. You don't want to make this section too cluttered, however, so restrict yourself to the most relevant information. Here's how to set up an email signature, along with more advice on what to include in it and what to leave off.