On the subject of tipjoy, a useful option would be to allow people to just collect recipients that they are interested in giving to, and then split $10 or whatever between them at the end of the month. I think this would have two advantages: reduce the effect of Clay Shirky's micropayment decision cost problem, and allow people to budget more easily (which will make them less scared of giving money).
(I was thinking of doing this until I heard of tipjoy, curse you :-).
Another idea - I don't know how difficult this would be - would be to have some way for websites to give freebies to people who have tipped more than, say $5 in total to anyone that month. The website owners would get two benefits: people would be more likely to tip them, and they would get more traffic (because you would provide an 'if you liked this...' feature to sites who did that). This interacts well with the 'split $X at the end of the month' feature, because tippers would then round up in order to get the freebies.
On the note of Tipjoy, thanks for making it. It's allowed me to take donations on my site without which I wouldn't've been able to otherwise (Due to PayPal's onerous terms of service).
I do have a suggestion. Make it so that the amount shown as pledged to a website only includes paid pledges.
As it stands, a bunch of people could say, pledge $100/200/whatever each to a cause to make it seem like that cause has already raised a lot of money, causing people who might legitimately donate to go, "Hey, they've already raised loads. I'll give to someone else".
Ooh. That'll be useful. I ended up having to make a new account for my latest donation drive, simply because on the last one, I'd taken in maybe.. $150 of paid pledges, but my 'amount' was near $400. :x
You can make the pledge drive centered around a blog post or twitter account. In the widgets set the targetUrl param, in addition to the user name param. The twitter tools are really useful too: http://tipjoy.com/twittertools
