take the new person on a quick "say hi" tour so they meet the people they will work with on a regular basis. If you have a small co-located team, they will pretty much know everyone in a matter of hours, if it is a large, spread-out team, they will need a bit more time, but they don't necessarily have to know every single person straight away.
integrate the new joiner straight away in normal project activities - use your regular meetings (eg. status meeting) to briefly introduce your new team member. Don't make everyone introduce themselves, your new team member won't remember half of it anyway.
provide new joiners with a who's who: this can be in the form of a team org chart, a physical board, a slide deck, the project social network page if you have one, etc. Basic information should include people's names and roles and a short one-liner about themselves. Photos help too, particularly if you have a large team or people are not co-located. It's helpful for the new joiner to visualize where they fit in.
make sure the new person has appropriate support on their first day: they should have the technical set-up (computer, tools, logins, etc.) ready for them, some form of induction pack (HR information, project background information, etc.). Make sure you or someone else is available to go for lunch with them, show them around, etc.
inform your team beforehand of the new arrival: this can be a simple email with the person's name, their role, a little background and what they will do, or a quick verbal announcement. I have seen projects where new people join with the project team having no clue that someone new was coming in, which makes it quite awkward and counter-productive for all parties.