怎样在博客上上载PPT文档

You have at least two options:

Option One (image files):

In PowerPoint, choose Save-as, and choose an image format (eg .png). When the system asks if you want all slides or just the current one, choose All.

Then upload all the image files that were created to your blog (I usually upload them to Picasa web albums first, and then just link from my blog to there)

Option Two (embedded presentation):
Upload the PowerPoint to Google Docs, making sure that the "Convert documents, presentations, and spreadsheets to the corresponding Google Docs formats"... option is ticked.

Once it's uploaded, choose Return to Google Docs

Open the presentation (by clicking on it)

Click on the Share button in the top RIGHT corner of the Presentation Editor, and choose Publish / Embed.

Click the Publish Document button.

Choose a player size (I like Medium for presentations that are going inside posts), how fast to advance slides, whether to start the presentation as soon as the player loads, and what to do when the last slide is reached.

Copy the HTML that is provided.

Return to Blogger.

If you want the presentation to go into a post, edit the post, go into Edit HTML mode, and paste in the HTML.
If you want the presentation to go into a gadget, go into Layout / Page Elements / Add a Gadget / HTML-Javascript, and paste the HTML into the Content field.