How do I know where to start looking for jobs online?

1.

Look at Hokies4Hire. After all, it is specifically for Virginia Tech students. Post your resume, but don't stop there. Look for jobs.

2.

Go the the category that matches your interests. Be sure to look at the career-field sites! There is probably more than one career grouping that matches your interests.

3.

From each list, read the brief descriptions and pick three or four sites to visit. Spend about five minutes on each. In five minutes you'll get a sense of whether a site has content and navigation that work for you.

4.

For sites you like, spend more time hunting for jobs. If you liked a site in five minutes, it's probably because you found jobs or other content of interest. How easy and lucky was that!?

5.

If you visited a site you don't like, go pick another and check it out for five minutes.

6.

See if you can find three to five sites that are useful to you. Perhaps find two general sites and three career-field sites, or other sites that match your interests. Note them, and use them to the fullest.

7.

Here's the most boring and completely obvious advice: Read what you see on the sites. Sometimes we miss good stuff, or we waste time hunting for something we can't find because we're skimming instead of reading.

8.

Most important: Remember that looking online is just one method of finding jobs and internships! Networking accounts for a significant portion of jobs and internships found. Career and job fairs — the opportunity to prepare and meet employer representatives in person — are a significant job/internship source for many students; however, not all career fields are represented at career fairs, and not all employers need to attend or choose to attend career fairs.

Because everyone and her cousin wants to start a website.
(And they all claim to be great.)
The .coms make money, typically by selling advertising.
The .orgs are typically not-for-profits that are running a service.
The .govs are government-hosted web sites.
Some will last; some will go away. Some are great; some not so.
Different job seekers have different needs, so there's room for variety at the table.
There are a lot of mustards in the grocery store; you read the ingredient list and pick the best ones for you.
Same with web sites; you're the consumer; use the sites you find useful.