ChargeOver - ChargeOver automates recurring billing, subscription billing, & payment acceptance. A SaaS that integrates with Xero, Quickbooks, & has an API. Free trial.

RTG Bills - Billing Made Easy: RTG Bills is software for legal billing and time tracking; for attorneys in law firms and sole practitioners; lawyer billing and accounting software; trust accounting

fusebill - Fusebill is the leading recurring billing and subscription management software for businesses. Try Fusebill for subscription billing made easy!

CaseFox - Web-based legal software for law firms and lawyers that has timekeeping, legal billing, expense tracking, time billing, trust accounting, case management, and many more features.

MinuteDock - Web-based time tracking software designed to integrate with the Xero accounting package.

TekLAW - New Wave Tek, home of TekLaw law office practice management software. Calendaring, billing, case management software.