What's a party without guests?! First things first, who to invite? The general rule with Bridal Showers is, if the bride is not inviting certain people to the wedding, you probably shouldn't invite them to the bridal shower. But usually the bride will give the maid of honor, or the bridesmaids, a list of people who she'd like to invite. If the bridesmaids are not hosting the shower, sometimes a close female relative will.
For this Unbridal Shower we used Paperless Post to send out electronic invites (Evites). I love the detail of the Paperless Post designs and how easy they are to customize. You even get the first couple free! QUALITY! 
It's also pretty typical to send out physical invites. The great thing about actually making or having invites printed is that they're easier to put in a scrapbook or give to the bride to keep. However, you do have to pay for postage. So for those brides who have mostly younger women at their bridal shower, the online method works fine. But you may have to print out a hard copy to send to any grandmothers who may not have the same access to email.
Find the Alice in Wonderland invite we used here: CLICK