When I mention money it's because in all probability you'll be putting in at least some real time appearances and will find yourself in the position of being asked for take-aways either from folks at a signing or personal appearance or from folks who put together 'goody bags' for conventions and conferences or maybe from bloggers who do giveaways for their readers.
So, while you can give away a copy of your Ebook easily online with no cost to you really, there are other things that work that are going to cost you something. And you probably want to keep a few things on hand so as to avoid the mad scramble of trying to get personalized items on short notice.
So let's talk about some ideas.
Bookmarks with a picture of your book cover and your info on them are great. They aren't the best for bookstores or conferences since almost everyone is handing them out there. But I woldn't say no either.
Postcards are a great item. They give you a bit more space to work with - book cover on one side, your book & personal info on the other, and maybe some space left to give to a fan with an autograph. And I've seen a lot of folks using them as bookmarks so that postcard might have a longer life than we might expect. VistaPrint is one resource, there are many others. You can even make a calendar there if you have enough material to creatively fill 12 'spots' of the year - then offer them as prizes or giveaways.
Buttons can be kind of cool and people frequently leave them pinned to things like totes, backpacks and vests. Thing is, don't get one too clunking large and avoid the very tiny. Design is very important here. Maybe just a bit of your cover and the website.
Magnets remain popular with people and they frequently find their way up onto refrigerators or stuck in cars or on the side of filing cabinets. That makes them a great giveaway and not too expensive either.
If your book is in hard copy, be prepared to give some copies away. Take advantage of the special price your publisher gives you and get them into the hands of reviewers, contest winners and the like. People love free stuff. Ebook? Even easier. And with an Ebook you can have cards printed up with a website where the book can be downloaded free.
There are plenty of other ways to promote yourself as well. You can blog and work with other bloggers to do some cross-promoting and cross-bloggng. If you don't want to have your own blog (and that's all right) you might be able to do the occasional 'guest blog' at a sight you like. Contact the site's owner and ask.
Do participate in some social networking - Twitter, Facebook, and others are out there. The goal is to make that persomal connection with your readers. To be real, and accessible.
What about personal appearances. Yep, it's a good idea to do some of those as well. The Book Tour isn't what it used to be, but getting your face out there is a big help. Book signings are okay, and can be fun, but not the first line of attack these days.
Book festivals are better. Conferences are good. School visits, if you write for that age group are good too.
You might think about getting a few T-shirts or coffee mugs with your book cover and info as giveaways. That can get pricy, but a few, as contest prizes or special bonuses can be a good idea. Cafe press is one place you can design and create your own 'stuff.' There are others, maybe even locally, look around. The advantage of Cafe Press is you can order as little as one or two and you can create a store right there online if you want to 'sell' those T-shirts and mugs, etc. as a sideline.