http://www.getharvest.com/
Expense reporting, time tracking and invoicing system. Starts from $12/mth for 1 user. $40/mth for 2-5 users. Pricey, but looks solid. Includes twitter based SMS/IM integration (neat). Feels quite ajaxy, nice design. Hat tip Jamie Cockburn.
http://www.myintervals.com/
Intervals is an online time tracking / invoicing system like FreshBooks / CashBoard. The web site seems dull. SSL is only available on $100/mth+ packages. $20/mth covers up to 10 projects, 500Mb, unlimited users.
http://www.getcashboard.com/
Online time tracking and invoicing tool like FreshBooks. Paid accounts from $12/mth, 7 projects, unlimited invoices, unbranded, online payments, pdf invoices. Looks good. Multi-currency support.
http://www.freshbooks.com/
FreshBooks is an online time tracking / invoicing system. It will generate invoices, accept payments via PayPal / Authorize.net / etc. It sends reminder emails and so on. Packages from $14 to $150 per month.