I use a self hosted invoicing system called FusionInvoice. It's free, open source, really basic, but works really well. I just created a subdomain on my profile site (so I have "rob79sdomain.com" as my portfolio and "billing.rob79sdomain.com" for invoicing).
Lets me create/send quotes to customers, let's them approve quotes, login to see their current outstanding payments (and make payments directly via paypal by just clicking a button on the open invoice), email invoices as PDF's, etc. It's not nearly as fancy as some of the subscription CRM's but it serves my needs.
It's not even really a CRM, it's a billing solution, but if you've been using an excel sheet (like I had) it's a big step up. You can create clients, save their profiles, categorize them, run reports, etc.
EDIT: Oh, I forgot to mention what is probably the most important feature for someone coming from an Excel spreadsheet: You can import the spreadsheet so you don't have to totally rebuild everything. You might have to tinker with your spreadsheet a little bit (ie. change column titles, etc) to get it to work, but it took me very little effort (and probably 1% of the time) to import rather than reenter/rebuild everything from scratch. Just go to the site I linked above, the very first page outlines the features better than I can.
DOUBLE EDIT: It looks like the developer (it's a one-person project but the guy who made it is really cool, I've chatted with him in the past and he's help me tweek things, added features the community recommended, etc) is working on a brand new version (FusionInvoice v2.0) but the current version (v1.3.4) is still working great for me. I'll definitely be upgrading to the new version once it's ready but am totally happy with the current version.