Many of my young friends and friends that are very new to blog have the same questions of how to add slide show and how to add pictures to their blog and what and who provide easy uploading of pictures.
There are many web albums available on the Web and I am currently using PICASA WEB ALBUMS as it's very user friendly and fast in uploading your pics.
Here's the link that you can sign up your account : Picasa Web Albums
What you can do :
1) Post photos and videos online
2) Share photos with friends and family
3) View and save your friends' photos
4) Add captions / comments to your photo
5) Create a photo album on certain topics (eg Otah Recipe), download all your otah photos, copy the embedded code and paste it on your blog......your slide show on otah is done.
My review on Picasa Web Albums :
1) Fast uploading speed
2) Seldom hang while uploading
3) You can choose multiple photos to upload and go on with your other job.
4) It will not slow down and slack your blog too much when your reader is scrolling your blog post.
5) The slide show appear smoothly.
6) I hope they can improve further for us to have more varieties of slide effect (eg pics moving in a circle, pics dropping from top, etc) rather then the current standard slide. However, the fast speed and user friendly features compromise this. I'm sure they will come out with better features soon.
Sign up an account and have fun with it.