Attention Deficit Disorder (ADHD) Test
http://psychcentral.com/addquiz.htm

The Computer Anxiety Scale
The Computer Anxiety Scale is a 16 item questionnaire that measures amount of computer anxiety. The test has a high internal consistency (r=.95) and performance on the Computer Anxiety Scale is negatively correlated with experience with computers (r=-.48) (Cohen & Waugh, 1989).
http://www.psych.uncc.edu/pagoolka/ComputerAnxiety.html

Alienation Test
http://webspace.ship.edu/cgboer/alientest.html

State Anxiety Inventory
Spielberger's State Anxiety Inventory consists of 20 items that ask how a person feels now, and reflects situational factors that may influence anxiety levels. Scores range from 20 to 80 and the higher the score the greater the level of anxiety.
http://www.psych.uncc.edu/pagoolka/SAI.html

Attachment Style Questionnaire
"Experiences in Close Relationships" questionnaire diagnoses your attachment style. After completing the test you get a good discussion of its implications with links for finding out more. They collect some personal data like age, marital status, ethnicity and nationality, so this data might be used in research, but they do not ask for names or other detailed identifying data.
http://www.web-research-design.net/cgi-bin/crq/crq.pl

Defensive Pessimism Questionnaire: Julie Norem
"Defensive pessimists lower their expectations to help prepare themselves for the worst. Then they mentally play through all the bad things that might happen. Though it sounds as if it might be depressing, defensive pessimism actually helps anxious people focus away from their emotions so that they can plan and act effectively." Quick checklist verifies your self-diagnosis. http://www.wellesley.edu/Psychology/Norem/Quiz/quiz.html

Depression: Goldberg Depression Inventory
"This scale is not designed to make a diagnosis of depression or take the place of a professional diagnosis." But it does tell you the extent to which you report symptoms typical of depression. Like the other screening tests on this page, it is transparent.
http://psychcentral.com/depquiz.htm

Depression Screening Test: National Mental Health Association
A quick, confidential, totally transparent test for symptoms of depression.
http://www.depression-screening.org/screeningtest/screeningtest.htm

Obsessive Compulsive Disorder Screening
Another transparent screening test, this one for OCD...basically a list of symptoms.
http://psychcentral.com/ocdquiz.htm

Personality: The Five Factor Personality Test (Big Five)
This one is shorter than the other two "big five" tests above, with some overlap in questions, but it is not a total duplicate which makes it good as a validity check. I found total agreement between these three tests on four of the dimensions, total disagreement and contradiction on one dimension, which is actually useful to know when evaluating the results.
http://users.wmin.ac.uk/~buchant/wwwffi/

Personality Type A/B: Jenkins
A "modified version of the Jenkins Activity Survey" from 1971. Find out whether you would be rated a Type A or Type B personality, or somewhere in between. Alas, they do not tell you the original type A/B construct fell apart when later research failed to replicate the original findings linking Type A to heart attacks. (Cynicism proved more predictive than time-urgency or activity level.) Therefore this test, while fun, illustrates the dangers of reification...treating a psychological construct as concrete and real, just because you can construct a test to measure it, when the "thing" being measured may not even exist as a meaningful psychological trait.
http://www.psych.uncc.edu/pagoolka/TypeAB.html

Shyness: Henderson/Zimbardo Shyness Questionnaire
Find your "ShyQ" or how shy you are. Results are provided immediately and compared with aggregated data from web participants.
http://www.shyness.com/qa2.html